checkpatch: add virt barriers

Add virt_ barriers to list of barriers to check for
presence of a comment.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Julian Calaby <julian.calaby@gmail.com>
Acked-by: Joe Perches <joe@perches.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>

scripts/checkpatch.pl

@@ -5133,7 +5133,8 @@ sub process {
 		}x;
 		my $all_barriers = qr{
 			(?:$barriers)|
-			smp_(?:$barrier_stems)
+			smp_(?:$barrier_stems)|
+			virt_(?:$barrier_stems)
 		}x;
 
 		if ($line =~ /\b(?:$all_barriers)\s*\(/) {