libpayload: Support unaligned pointers for memset

libpayload: Support unaligned pointers for memset

The optimization of the memset() function introduced by commit
dbadb1dd634c8c9419215ade0666a7fb69a4447b (libpayload: Reorder default
memcpy, speed up memset and memcmp) is provoking an issue on x86
platform when compiling without the CONFIG_GPL option.

GCC is making use of the movdqa instruction to copy words.  This
instruction can raise a "General Protection Fault Exception" when it
is called on a non-aligned address argument.

Change-Id: I73382a76a4399d8e78244867f2ebb1dca176a6bf
Signed-off-by: Jeremy Compostella <jeremy.compostella@intel.com>
Reviewed-on: https://review.coreboot.org/20524
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>