qcacmn: improve mboxping TX t-put for SDIO project

qcacld-2.0 to qcacmn propagation

Return HTC_SEND_FULL_KEEP directly in epping_tx_queue_full function
and give nodrop pkts higher priority over normal pkts

Change-Id: Ib36e1a9f34eb9054b12f0e8ba54a86ace7d6c8f8
CRs-Fixed: 990726

htc/htc.c

@@ -266,6 +266,7 @@ HTC_HANDLE htc_create(void *ol_sc, HTC_INIT_INFO *pInfo, qdf_device_t osdev,
 	qdf_spinlock_create(&target->HTCRxLock);
 	qdf_spinlock_create(&target->HTCTxLock);
 	qdf_spinlock_create(&target->HTCCreditLock);
+	target->is_nodrop_pkt = false;
 
 	do {
 		qdf_mem_copy(&target->HTCInitInfo, pInfo,