mac802154: llsec: fold useless return value check

llsec_do_encrypt will never return a positive value, so the restriction
to 0-or-negative on return is useless.
Signed-off-by: NPhoebe Buckheister <phoebe.buckheister@itwm.fraunhofer.de>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/mac802154/llsec.c

@@ -773,7 +773,7 @@ int mac802154_llsec_encrypt(struct mac802154_llsec *sec, struct sk_buff *skb)
 	rc = llsec_do_encrypt(skb, sec, &hdr, key);
 	llsec_key_put(key);
 
-	return rc < 0 ? rc : 0;
+	return rc;
 
 fail_read:
 	read_unlock_bh(&sec->lock);