microcode/amd: distinguish old and mismatched ucode in microcode_fits()

microcode/amd: distinguish old and mismatched ucode in microcode_fits()

Sometimes, an ucode with a level lower than or equal to current CPU's
patch level is useful. For example, to work around a broken bios which
only loads ucode for BSP, when BSP parses an ucode blob during bootup,
it is better to save an ucode with lower or equal level for APs

No functional change is made in this patch. But following patch would
handle "old ucode" and "mismatched ucode" separately.

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