IB/mlx4: 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>
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

drivers/infiniband/hw/mlx4/cq.c

@@ -768,11 +768,13 @@ static int mlx4_ib_poll_one(struct mlx4_ib_cq *cq,
 		switch (cqe->owner_sr_opcode & MLX4_CQE_OPCODE_MASK) {
 		case MLX4_OPCODE_RDMA_WRITE_IMM:
 			wc->wc_flags |= IB_WC_WITH_IMM;
+			/* fall through */
 		case MLX4_OPCODE_RDMA_WRITE:
 			wc->opcode    = IB_WC_RDMA_WRITE;
 			break;
 		case MLX4_OPCODE_SEND_IMM:
 			wc->wc_flags |= IB_WC_WITH_IMM;
+			/* fall through */
 		case MLX4_OPCODE_SEND:
 		case MLX4_OPCODE_SEND_INVAL:
 			wc->opcode    = IB_WC_SEND;

drivers/infiniband/hw/mlx4/mcg.c

@@ -944,6 +944,7 @@ int mlx4_ib_mcg_multiplex_handler(struct ib_device *ibdev, int port,
 	switch (sa_mad->mad_hdr.method) {
 	case IB_MGMT_METHOD_SET:
 		may_create = 1;
+		/* fall through */
 	case IB_SA_METHOD_DELETE:
 		req = kzalloc(sizeof *req, GFP_KERNEL);
 		if (!req)