IB/qib: 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: Bart Van Assche <bart.vanassche@wdc.com>
Acked-by: Mike Marciniszyn <infinipath@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

drivers/infiniband/hw/qib/qib_mad.c

@@ -434,6 +434,7 @@ static int check_mkey(struct qib_ibport *ibp, struct ib_smp *smp, int mad_flags)
 			/* 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/qib/qib_rc.c

@@ -1869,7 +1869,7 @@ void qib_rc_rcv(struct qib_ctxtdata *rcd, struct ib_header *hdr,
 		qp->r_rcv_len = 0;
 		if (opcode == OP(SEND_ONLY))
 			goto no_immediate_data;
-		/* FALLTHROUGH for SEND_ONLY_WITH_IMMEDIATE */
+		/* fall through -- 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/qib/qib_sdma.c

@@ -808,7 +808,7 @@ void __qib_sdma_process_event(struct qib_pportdata *ppd,
 			 * bringing the link up with traffic active on
 			 * 7220, e.g. */
 			ss->go_s99_running = 1;
-			/* fall through and start dma engine */
+			/* fall through -- and start dma engine */
 		case qib_sdma_event_e10_go_hw_start:
 			/* This reference means the state machine is started */
 			sdma_get(&ppd->sdma_state);