haswell: Update microcode revision

CPUID 306C3 Haswell MOB C-0 microcode to 12h
CPUID 40651 Haswell ULT C-0 microcode to 15h

localhost ~ # grep microcode /proc/cpuinfo
microcode       : 0x15
microcode       : 0x15

Change-Id: Ibdfe2b8ef0969b1ccc6dd1642a9fc352b5d11f27
Signed-off-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/63045
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: http://review.coreboot.org/4378
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <patrick@georgi-clan.de>
4 files changed