libfdt requires memchr. Add missing function to libc.
Change-Id: I872026559d16a352f350147c9d7c4be97456a99f
Signed-off-by: Philipp Hug <philipp@hug.cx>
Reviewed-on: https://review.coreboot.org/c/31354
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>