RDMA/bnxt_re: 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>
Cc: Somnath Kotur <somnath.kotur@broadcom.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

drivers/infiniband/hw/bnxt_re/qplib_fp.c

@@ -1360,7 +1360,7 @@ int bnxt_qplib_post_send(struct bnxt_qplib_qp *qp,
 
 			break;
 		}
-		/* else, just fall thru */
+		/* fall thru */
 	case BNXT_QPLIB_SWQE_TYPE_SEND_WITH_IMM:
 	case BNXT_QPLIB_SWQE_TYPE_SEND_WITH_INV:
 	{