block: Mark expected switch fall-throughs

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

This patch fixes the following warnings:

drivers/block/drbd/drbd_int.h:1774:6: warning: this statement may fall through [-Wimplicit-fallthrough=]
drivers/block/drbd/drbd_int.h:1774:6: warning: this statement may fall through [-Wimplicit-fallthrough=]
drivers/block/drbd/drbd_int.h:1774:6: warning: this statement may fall through [-Wimplicit-fallthrough=]
drivers/block/drbd/drbd_int.h:1774:6: warning: this statement may fall through [-Wimplicit-fallthrough=]
drivers/block/drbd/drbd_int.h:1774:6: warning: this statement may fall through [-Wimplicit-fallthrough=]
drivers/block/drbd/drbd_receiver.c:3093:6: warning: this statement may fall through [-Wimplicit-fallthrough=]
drivers/block/drbd/drbd_receiver.c:3120:6: warning: this statement may fall through [-Wimplicit-fallthrough=]
drivers/block/drbd/drbd_req.c:856:6: warning: this statement may fall through [-Wimplicit-fallthrough=]

Warning level 3 was used: -Wimplicit-fallthrough=3

This patch is part of the ongoing efforts to enable
-Wimplicit-fallthrough
Reviewed-by: NChaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
Acked-by: NRoland Kammerer <roland.kammerer@linbit.com>
Signed-off-by: NGustavo A. R. Silva <gustavo@embeddedor.com>

drivers/block/drbd/drbd_int.h

@@ -1778,7 +1778,7 @@ static inline void __drbd_chk_io_error_(struct drbd_device *device,
 				_drbd_set_state(_NS(device, disk, D_INCONSISTENT), CS_HARD, NULL);
 			break;
 		}
-		/* NOTE fall through for DRBD_META_IO_ERROR or DRBD_FORCE_DETACH */
+		/* fall through - for DRBD_META_IO_ERROR or DRBD_FORCE_DETACH */
 	case EP_DETACH:
 	case EP_CALL_HELPER:
 		/* Remember whether we saw a READ or WRITE error.

drivers/block/drbd/drbd_receiver.c

@@ -3094,7 +3094,7 @@ static int drbd_asb_recover_0p(struct drbd_peer_device *peer_device) __must_hold
 			rv =  1;
 			break;
 		}
-		/* Else fall through to one of the other strategies... */
+		/* Else fall through - to one of the other strategies... */
 	case ASB_DISCARD_OLDER_PRI:
 		if (self == 0 && peer == 1) {
 			rv = 1;
@@ -3119,7 +3119,7 @@ static int drbd_asb_recover_0p(struct drbd_peer_device *peer_device) __must_hold
 		}
 		if (after_sb_0p == ASB_DISCARD_ZERO_CHG)
 			break;
-		/* else: fall through */
+		/* else, fall through */
 	case ASB_DISCARD_LEAST_CHG:
 		if	(ch_self < ch_peer)
 			rv = -1;

drivers/block/drbd/drbd_req.c

@@ -866,7 +866,7 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
 			} /* else: FIXME can this happen? */
 			break;
 		}
-		/* else, fall through to BARRIER_ACKED */
+		/* else, fall through - to BARRIER_ACKED */
 
 	case BARRIER_ACKED:
 		/* barrier ack for READ requests does not make sense */

drivers/block/rsxx/core.c

@@ -439,6 +439,7 @@ static void card_state_change(struct rsxx_cardinfo *card,
 		 * Fall through so the DMA devices can be attached and
 		 * the user can attempt to pull off their data.
 		 */
+		/* fall through */
 	case CARD_STATE_GOOD:
 		st = rsxx_get_card_size8(card, &card->size8);
 		if (st)