cxgb3/l2t: Mark expected switch fall-through

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

Addresses-Coverity-ID: 114780 ("Missing break in switch")
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/chelsio/cxgb3/l2t.c

@@ -136,6 +136,7 @@ again:
 		if (e->state == L2T_STATE_STALE)
 			e->state = L2T_STATE_VALID;
 		spin_unlock_bh(&e->lock);
+		/* fall through */
 	case L2T_STATE_VALID:	/* fast-path, send the packet on */
 		return cxgb3_ofld_send(dev, skb);
 	case L2T_STATE_RESOLVING: