iommu/vt-d: Simplify check in identity_mapping()

The function only has one call-site and there it is never called with
dummy or deferred devices. Simplify the check in the function to
account for that.

Fixes: 1ee0186b ("iommu/vt-d: Refactor find_domain() helper")
Cc: stable@vger.kernel.org # v5.5
Reviewed-by: NJerry Snitselaar <jsnitsel@redhat.com>
Acked-by: NLu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: NJoerg Roedel <jroedel@suse.de>

drivers/iommu/intel-iommu.c

@@ -2916,7 +2916,7 @@ static int identity_mapping(struct device *dev)
 	struct device_domain_info *info;
 
 	info = dev->archdata.iommu;
-	if (info && info != DUMMY_DEVICE_DOMAIN_INFO && info != DEFER_DEVICE_DOMAIN_INFO)
+	if (info)
 		return (info->domain == si_domain);
 
 	return 0;