x86/microcode_core_early.c: Define interfaces for early loading ucode

Define interfaces load_ucode_bsp() and load_ucode_ap() to load ucode on BSP and
AP in early boot time. These are generic interfaces. Internally they call
vendor specific implementations.

Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Link: http://lkml.kernel.org/r/1356075872-3054-6-git-send-email-fenghua.yu@intel.com
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>