drivers/intel/fsp/fsp_util.c: Remove attribute,optimize("O0")

This is not actually required. Tested on 'minnow max' hardware as
well as compared the asm of the optimized and non-optimized. Thanks Martin!

Change-Id: I06e71876c3a3a15101013623797c2ebbf449756d
Signed-off-by: Edward O'Callaghan <eocallaghan@alterapraxis.com>
Found-by: Clang
Reviewed-on: http://review.coreboot.org/7694
Reviewed-by: Martin Roth <gaumless@gmail.com>
Tested-by: build bot (Jenkins)
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>