x86, microcode, amd: Refactor functions to prepare for early loading

In preparation work for early loading, refactor some common functions
that will be shared, and move some struct defines to a common header file.

Signed-off-by: Jacob Shin <jacob.shin@amd.com>
Link: http://lkml.kernel.org/r/1369940959-2077-4-git-send-email-jacob.shin@amd.com


Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>