qcacmn: Microsecond time stamping for hw tx latency stats

Use microsecond timestamping for the tx descriptors
for capturing the latencies more accurately. It will help
to determine the appropriate bucket.

Change-Id: I216e083a7c89b01b6f2f384c1c0a85ca323d3a3e
CRs-Fixed: 3165153

qdf/inc/qdf_time.h

@@ -83,6 +83,14 @@ qdf_ktime_t qdf_ktime_add_ns(qdf_ktime_t ktime, int64_t ns);
  */
 int64_t qdf_ktime_to_ms(qdf_ktime_t ktime);
 
+/**
+ * qdf_ktime_to_us - Convert the qdf_ktime_t object into microseconds
+ * @ktime: time as qdf_ktime_t object
+ *
+ * Return: qdf_ktime_t in microseconds
+ */
+int64_t qdf_ktime_to_us(qdf_ktime_t ktime);
+
 /**
  * qdf_ktime_to_ns - Convert the qdf_ktime_t object into nanoseconds
  * @ktime: time as qdf_ktime_t object