drbd: Fix fall-through warnings for Clang

In preparation to enable -Wimplicit-fallthrough for Clang, fix a couple
of warnings by explicitly adding a break statement instead of just
letting the code fall through to the next, and by adding a fallthrough
pseudo-keyword in places whre the code is intended to fall through.

Link: https://github.com/KSPP/linux/issues/115Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/drbd/drbd_receiver.c

@@ -5863,6 +5863,7 @@ static int got_NegRSDReply(struct drbd_connection *connection, struct packet_inf
 		switch (pi->cmd) {
 		case P_NEG_RS_DREPLY:
 			drbd_rs_failed_io(device, sector, size);
+			break;
 		case P_RS_CANCEL:
 			break;
 		default:

drivers/block/drbd/drbd_req.c

@@ -753,6 +753,7 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
 
 	case WRITE_ACKED_BY_PEER_AND_SIS:
 		req->rq_state |= RQ_NET_SIS;
+		fallthrough;
 	case WRITE_ACKED_BY_PEER:
 		/* Normal operation protocol C: successfully written on peer.
 		 * During resync, even in protocol != C,