qcacmn: Fix implicit-fallthrough compile error casued by gcc 9.3

Compiling with gcc 9.3 will cause many implicit-fallthrough
compile errors.

Fix is to add keyword fallthrough to resolve such compile error.

Change-Id: I2e7dd1525861d951e3be44f6665e149499f0f5d6
CRs-Fixed: 2785178

htc/htc_send.c

@@ -757,6 +757,7 @@ static QDF_STATUS htc_issue_packets(HTC_TARGET *target,
 					    (pEndpoint) < 1)
 						break;
 				}
+				/* fallthrough */
 			case QDF_BUS_TYPE_USB:
 				htc_issue_packets_bundle(target,
 							pEndpoint,
@@ -1599,6 +1600,7 @@ static enum HTC_SEND_QUEUE_RESULT htc_try_send(HTC_TARGET *target,
 					pEndpoint->total_num_requeues++;
 					pEndpoint->num_requeues_warn = 0;
 				}
+				/* fallthrough */
 			default:
 				QDF_TRACE(QDF_MODULE_ID_HIF, QDF_TRACE_LEVEL_INFO,
 					  "htc_issue_packets, failed status:%d"