x86/ucode: fix Intel case of resume handling on boot CPU

Checking the stored version doesn't tell us anything about the need to
apply the update (during resume, what is stored doesn't necessarily
match what is loaded).

Note that the check can be removed altogether because once switched to
use what was read from the CPU (uci->cpu_sig.rev, as used in the
subsequent pr_debug()), it would become redundant with the checks that
lead to microcode_update_match() returning the indication that an
update should be applied.

Note further that this was not an issue on APs since they start with
uci->mc.mc_intel being NULL.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
Tested-by: Ben Guthro <ben@xxxxxxxxxx>

--- a/xen/arch/x86/microcode_intel.c
+++ b/xen/arch/x86/microcode_intel.c
@@ -261,8 +261,6 @@ static int get_matching_microcode(const 
     }
     return 0;
  find:
-    if ( uci->mc.mc_intel && uci->mc.mc_intel->hdr.rev >= mc_header->rev )
-        return 0;
     pr_debug("microcode: CPU%d found a matching microcode update with"
              " version %#x (current=%#x)\n",
              cpu, mc_header->rev, uci->cpu_sig.rev);