net: remove the unnecessary check in cipso_v4_doi_free

The commit 733c99ee ("net: fix NULL pointer reference in
cipso_v4_doi_free") was merged by a mistake, this patch try
to cleanup the mess.

And we already have the commit e842cb60 ("net: fix NULL
pointer reference in cipso_v4_doi_free") which fixed the root
cause of the issue mentioned in it's description.
Suggested-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Michael Wang <yun.wang@linux.alibaba.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/cipso_ipv4.c

@@ -465,16 +465,14 @@ void cipso_v4_doi_free(struct cipso_v4_doi *doi_def)
 	if (!doi_def)
 		return;
 
-	if (doi_def->map.std) {
-		switch (doi_def->type) {
-		case CIPSO_V4_MAP_TRANS:
-			kfree(doi_def->map.std->lvl.cipso);
-			kfree(doi_def->map.std->lvl.local);
-			kfree(doi_def->map.std->cat.cipso);
-			kfree(doi_def->map.std->cat.local);
-			kfree(doi_def->map.std);
-			break;
-		}
+	switch (doi_def->type) {
+	case CIPSO_V4_MAP_TRANS:
+		kfree(doi_def->map.std->lvl.cipso);
+		kfree(doi_def->map.std->lvl.local);
+		kfree(doi_def->map.std->cat.cipso);
+		kfree(doi_def->map.std->cat.local);
+		kfree(doi_def->map.std);
+		break;
 	}
 	kfree(doi_def);
 }