net/mlx4/en_rx: Mark expected switch fall-throughs

In preparation to enabling -Wimplicit-fallthrough, mark switch cases
where we are expecting to fall through.

Addresses-Coverity-ID: 114794 ("Missing break in switch")
Addresses-Coverity-ID: 114795 ("Missing break in switch")
Signed-off-by: NGustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlx4/en_rx.c

@@ -795,8 +795,10 @@ int mlx4_en_process_rx_cq(struct net_device *dev, struct mlx4_en_cq *cq, int bud
 				goto xdp_drop_no_cnt; /* Drop on xmit failure */
 			default:
 				bpf_warn_invalid_xdp_action(act);
+				/* fall through */
 			case XDP_ABORTED:
 				trace_xdp_exception(dev, xdp_prog, act);
+				/* fall through */
 			case XDP_DROP:
 				ring->xdp_drop++;
 xdp_drop_no_cnt: