net: rxrpc: mark expected switch fall-throughs

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>
diff --git a/net/rxrpc/input.c b/net/rxrpc/input.c
index e56e23e..1e37eb1 100644
--- a/net/rxrpc/input.c
+++ b/net/rxrpc/input.c
@@ -1125,6 +1125,7 @@
 	case RXRPC_PACKET_TYPE_BUSY:
 		if (sp->hdr.flags & RXRPC_CLIENT_INITIATED)
 			goto discard;
+		/* Fall through */
 
 	case RXRPC_PACKET_TYPE_DATA:
 		if (sp->hdr.callNumber == 0)