IB/hfi1: Suppress gcc 7 fall-through complaints

Avoid that gcc 7 reports the following warning when building with W=1:

warning: this statement may fall through [-Wimplicit-fallthrough=]
Signed-off-by: NBart Van Assche <bart.vanassche@wdc.com>
Reviewed-by: NDennis Dalessandro <dennis.dalessandro@intel.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: NDoug Ledford <dledford@redhat.com>

drivers/infiniband/hw/hfi1/mad.c

@@ -711,6 +711,7 @@ static int check_mkey(struct hfi1_ibport *ibp, struct ib_mad_hdr *mad,
 			/* Bad mkey not a violation below level 2 */
 			if (ibp->rvp.mkeyprot < 2)
 				break;
+			/* fall through */
 		case IB_MGMT_METHOD_SET:
 		case IB_MGMT_METHOD_TRAP_REPRESS:
 			if (ibp->rvp.mkey_violations != 0xFFFF)

drivers/infiniband/hw/hfi1/rc.c

@@ -2175,7 +2175,7 @@ void hfi1_rc_rcv(struct hfi1_packet *packet)
 			goto no_immediate_data;
 		if (opcode == OP(SEND_ONLY_WITH_INVALIDATE))
 			goto send_last_inv;
-		/* FALLTHROUGH for SEND_ONLY_WITH_IMMEDIATE */
+		/* FALLTHROUGH -- for SEND_ONLY_WITH_IMMEDIATE */
 	case OP(SEND_LAST_WITH_IMMEDIATE):
 send_last_imm:
 		wc.ex.imm_data = ohdr->u.imm_data;

drivers/infiniband/hw/hfi1/sdma.c

@@ -2593,7 +2593,7 @@ static void __sdma_process_event(struct sdma_engine *sde,
 			 * 7220, e.g.
 			 */
 			ss->go_s99_running = 1;
-			/* fall through and start dma engine */
+			/* fall through -- and start dma engine */
 		case sdma_event_e10_go_hw_start:
 			/* This reference means the state machine is started */
 			sdma_get(&sde->state);
@@ -3016,6 +3016,7 @@ static void __sdma_process_event(struct sdma_engine *sde,
 		case sdma_event_e60_hw_halted:
 			need_progress = 1;
 			sdma_err_progress_check_schedule(sde);
+			/* fall through */
 		case sdma_event_e90_sw_halted:
 			/*
 			* SW initiated halt does not perform engines