LICENSE: add license for zmodem

document the license in the LICENSE file

Signed-off-by: Alin Jerpelea <alin.jerpelea@sony.com>

LICENSE

@@ -1354,3 +1354,87 @@ apps/system/ubloxmodem/ubloxmodem.h
  LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
  ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  POSSIBILITY OF SUCH DAMAGE.
+
+apps/system/zmodem/host/crc16.c
+===============================
+
+   Copyright (C) 2013 Gregory Nutt. All rights reserved.
+
+ References:
+
+   crc16_tab calculated by Mark G. Mendel, Network Systems Corporation.
+   crc16part() logic derived from article Copyright (C) 1986 Stephen Satchell.
+
+ "Programmers may incorporate any or all code into their programs,
+  giving proper credit within the source. Publication of the
+  source routines is permitted so long as proper credit is given
+  to Stephen Satchell, Satchell Evaluations and Chuck Forsberg,
+  Omen Technology."
+
+ Re-released under the Modified BSD license which, I believe, is consistent with the
+ original authors' intent:
+
+ Redistribution and use in source and binary forms, with or without
+ modification, are permitted provided that the following conditions
+ are met:
+
+ 1. Redistributions of source code must retain the above copyright
+    notice, this list of conditions and the following disclaimer.
+ 2. Redistributions in binary form must reproduce the above copyright
+    notice, this list of conditions and the following disclaimer in
+    the documentation and/or other materials provided with the
+    distribution.
+ 3. Neither the name NuttX nor the names of its contributors may be
+    used to endorse or promote products derived from this software
+    without specific prior written permission.
+
+ THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ POSSIBILITY OF SUCH DAMAGE.
+
+apps/system/zmodem/host/crc32.c
+=================================
+
+   Copyright (C) 2013 Gregory Nutt. All rights reserved.
+
+ The logic in this file was developed by Gary S. Brown:
+
+   COPYRIGHT (C) 1986 Gary S. Brown.  You may use this program, or code or tables
+   extracted from it, as desired without restriction.
+
+ First, the polynomial itself and its table of feedback terms.  The polynomial is:
+
+    X^32+X^26+X^23+X^22+X^16+X^12+X^11+X^10+X^8+X^7+X^5+X^4+X^2+X^1+X^0
+
+ Note that we take it "backwards" and put the highest-order term in the lowest-order bit.
+ The X^32 term is "implied"; the LSB is the X^31 term, etc.  The X^0 term (usually shown
+ as "+1") results in the MSB being 1
+
+ Note that the usual hardware shift register implementation, which is what we're using
+ (we're merely optimizing it by doing eight-bit chunks at a time) shifts bits into the
+ lowest-order term.  In our implementation, that means shifting towards the right.  Why
+ do we do it this way?  Because the calculated CRC must be transmitted in order from
+ highest-order term to lowest-order term.  UARTs transmit characters in order from LSB
+ to MSB.  By storing the CRC this way we hand it to the UART in the order low-byte to
+ high-byte; the UART sends each low-bit to hight-bit; and the result is transmission bit
+ by bit from highest- to lowest-order term without requiring any bit shuffling on our
+ part.  Reception works similarly
+
+ The feedback terms table consists of 256, 32-bit entries.  Notes
+
+ - The table can be generated at runtime if desired; code to do so is shown later.  It
+   might not be obvious, but the feedback terms simply represent the results of eight
+   shift/xor operations for all combinations of data and CRC register values
+
+ - The values must be right-shifted by eight bits by the updcrc logic; the shift must
+   be u_(bring in zeroes).  On some hardware you could probably optimize the shift in
+   assembler by using byte-swap instructions polynomial