microcode/intel: extend microcode_update_match()

microcode/intel: extend microcode_update_match()

to a more generic function. So that it can be used alone to check
an update against the CPU signature and current update revision.

Note that enum microcode_match_result will be used in common code
(aka microcode.c), it has been placed in the common header. And
constifying the parameter of microcode_sanity_check() such that it
can be called by microcode_update_match().

Signed-off-by: Chao Gao <chao.gao@intel.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>