net: af_unix: mark expected switch fall-through

In preparation to enabling -Wimplicit-fallthrough, mark switch cases
where we are expecting to fall through.
Signed-off-by: Gustavo A. R. Silva <garsilva@embeddedor.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/unix/af_unix.c

@@ -814,6 +814,7 @@ static int unix_create(struct net *net, struct socket *sock, int protocol,
 		 */
 	case SOCK_RAW:
 		sock->type = SOCK_DGRAM;
+		/* fall through */
 	case SOCK_DGRAM:
 		sock->ops = &unix_dgram_ops;
 		break;