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: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
diff --git a/net/mac802154/rx.c b/net/mac802154/rx.c
index 42e9672..446e130 100644
--- a/net/mac802154/rx.c
+++ b/net/mac802154/rx.c
@@ -217,8 +217,7 @@
 		break;
 	}
 
-	if (skb)
-		kfree_skb(skb);
+	kfree_skb(skb);
 }
 
 static void