qcacmn: Add function to calculate hardware Tx delay

Define a new function to calculate HW delay so that same logic
can be used to calculate delay by other modules.

Change-Id: Id3740bcaa2cd558b89ab02d8e88d5947eb5997b1
CRs-Fixed: 3198305

hal/wifi3.0/hal_tx.h

@@ -233,7 +233,7 @@ struct hal_tx_completion_status {
 	uint8_t transmit_cnt;
 	uint8_t tid;
 	uint16_t peer_id;
-#if defined(WLAN_FEATURE_TSF_UPLINK_DELAY) || defined(CONFIG_SAWF)
+#if defined(WLAN_FEATURE_TSF_UPLINK_DELAY) || defined(QCA_PEER_EXT_STATS)
 	uint32_t buffer_timestamp:19;
 #endif
 };