mac802154: Delete an unnecessary check before the function call "kfree_skb"

The kfree_skb() function tests whether its argument is NULL and then
returns immediately. Thus the test around the call is not needed.

This issue was detected by using the Coccinelle software.
Signed-off-by: NMarkus Elfring <elfring@users.sourceforge.net>
Signed-off-by: NMarcel Holtmann <marcel@holtmann.org>

net/mac802154/rx.c

@@ -217,8 +217,7 @@ __ieee802154_rx_handle_packet(struct ieee802154_local *local,
 		break;
 	}
 
-	if (skb)
-		kfree_skb(skb);
+	kfree_skb(skb);
 }
 
 static void