cmd: printf: import busybox-1.33.1 printf.c

Import printf.c from the Busybox project, which provides Bash like
format string handling.

  src-url: https://git.busybox.net/busybox/
  commit bcc5b0e6caca6c7602a6a41f "Bump version to 1.33.1"
  version: 1.33.1

Signed-off-by: Roland Gaudig <roland.gaudig@weidmueller.com>