net: smc_close: mark expected switch fall-through

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

Notice that in this particular case I placed the "fall through" comment
on its own line, which is what GCC is expecting to find.
Signed-off-by: NGustavo A. R. Silva <garsilva@embeddedor.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/smc/smc_close.c

@@ -360,7 +360,8 @@ static void smc_close_passive_work(struct work_struct *work)
 	case SMC_PEERCLOSEWAIT1:
 		if (rxflags->peer_done_writing)
 			sk->sk_state = SMC_PEERCLOSEWAIT2;
-		/* fall through to check for closing */
+		/* fall through */
+		/* to check for closing */
 	case SMC_PEERCLOSEWAIT2:
 	case SMC_PEERFINCLOSEWAIT:
 		if (!smc_cdc_rxed_any_close(&smc->conn))