libpayload: Fix default_memmove() implementation

If I wanted to fill the whole memory address space with one byte, I
wouldn't try it that subtle.

With size_t beeing unsigned the loop condition >= 0 was always true.

Change-Id: Idee6a4901f6697093c88bda354b5e43066c0d948
Signed-off-by: Nico Huber <nico.huber@secunet.com>
Reviewed-on: http://review.coreboot.org/11286
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Tested-by: build bot (Jenkins)
1 file changed