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: Phoebe Buckheister <phoebe.buckheister@itwm.fraunhofer.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/mac802154/llsec.c b/net/mac802154/llsec.c
index 6edcb20..08d08cb 100644
--- a/net/mac802154/llsec.c
+++ b/net/mac802154/llsec.c
@@ -773,7 +773,7 @@
 	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);