qcacmn: Optimize dp_pkt_add_timestamp call to save CPU load

get_log_timestamp API is being called unconditionally when passed as
an argument to dp_pkt_add_timestamp (even for empty calls) from
dp_tx_hw_enqueue_li. This adds significant load on CPU, hence avoid
get_log_timestamp call by using preprocessor directive.

Change-Id: I1d988597e28b755a767a267d1b578b2bcedc324e
CRs-Fixed: 3150795

dp/wifi3.0/li/dp_li.h

@@ -132,12 +132,7 @@ void dp_pkt_add_timestamp(struct dp_vdev *vdev,
  */
 void dp_pkt_get_timestamp(uint64_t *time);
 #else
-static inline
-void dp_pkt_add_timestamp(struct dp_vdev *vdev,
-			  enum qdf_pkt_timestamp_index index, uint64_t time,
-			  qdf_nbuf_t nbuf)
-{
-}
+#define dp_pkt_add_timestamp(vdev, index, time, nbuf)
 
 static inline
 void dp_pkt_get_timestamp(uint64_t *time)