dm raid: fix compat_features validation

In ecbfb9f ("dm raid: add raid level takeover support") a new
compatible feature flag was added.  Validation for these compat_features
was added but this only passes for new raid mappings with this feature
flag.  This causes previously created raid mappings to be failed at
import.

Check compat_features for the only valid combination.

Fixes: ecbfb9f ("dm raid: add raid level takeover support")
Cc: stable@vger.kernel.org # v4.8
Signed-off-by: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Heinz Mauelshagen <heinzm@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

drivers/md/dm-raid.c

@@ -2258,7 +2258,8 @@ static int super_validate(struct raid_set *rs, struct md_rdev *rdev)
 	if (!mddev->events && super_init_validation(rs, rdev))
 		return -EINVAL;
 
-	if (le32_to_cpu(sb->compat_features) != FEATURE_FLAG_SUPPORTS_V190) {
+	if (le32_to_cpu(sb->compat_features) &&
+	    le32_to_cpu(sb->compat_features) != FEATURE_FLAG_SUPPORTS_V190) {
 		rs->ti->error = "Unable to assemble array: Unknown flag(s) in compatible feature flags";
 		return -EINVAL;
 	}