x86/Kconfig: Make early microcode loading a configuration feature

MICROCODE_INTEL_LIB, MICROCODE_INTEL_EARLY, and MICROCODE_EARLY are three new
configurations to enable or disable the feature.

Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Link: http://lkml.kernel.org/r/1356075872-3054-13-git-send-email-fenghua.yu@intel.com


Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>