dtc: migrate parser to implicit rules

Cc: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Arnaud Lacombe <lacombar@gmail.com>

scripts/dtc/Makefile

@@ -25,31 +25,5 @@ HOSTCFLAGS_dtc-lexer.lex.o := $(HOSTCFLAGS_DTC)
 HOSTCFLAGS_dtc-parser.tab.o := $(HOSTCFLAGS_DTC)
 
 # dependencies on generated files need to be listed explicitly
-$(obj)/dtc-parser.tab.o: $(obj)/dtc-parser.tab.c $(obj)/dtc-parser.tab.h
-$(obj)/dtc-lexer.lex.o:  $(obj)/dtc-lexer.lex.c $(obj)/dtc-parser.tab.h
+$(obj)/dtc-lexer.lex.o: $(obj)/dtc-parser.tab.h
 
-targets += dtc-parser.tab.c dtc-lexer.lex.c
-
-clean-files += dtc-parser.tab.h
-
-# GENERATE_PARSER := 1		# Uncomment to rebuild flex/bison output
-
-ifdef GENERATE_PARSER
-
-BISON = bison
-FLEX = flex
-
-quiet_cmd_bison = BISON   $@
-      cmd_bison = $(BISON) -o$@ -d $<; cp $@ $@_shipped
-quiet_cmd_flex = FLEX    $@
-      cmd_flex = $(FLEX) -o$@ $<; cp $@ $@_shipped
-
-$(obj)/dtc-parser.tab.c: $(src)/dtc-parser.y FORCE
-        $(call if_changed,bison)
-
-$(obj)/dtc-parser.tab.h: $(obj)/dtc-parser.tab.c
-
-$(obj)/dtc-lexer.lex.c: $(src)/dtc-lexer.l FORCE
-        $(call if_changed,flex)
-
-endif