qcacmn: Add API to get TX pending in WoW state

This change is used to provide an API for PMO module to
check whether there are pending TX frames before HOST sends
wake up indication to FW. PMO module uses this to indicate
FW whehter to discard HWDTIM.

Change-Id: Icc3271e87e376e3313fddc5f4f99e39daeaf6af7
CRs-Fixed: 3046947

dp/wifi3.0/dp_main.c

@@ -11218,6 +11218,7 @@ void dp_flush_ring_hptp(struct dp_soc *soc, hal_ring_handle_t hal_srng)
 		hal_srng_access_end(soc->hal_soc, hal_srng);
 
 		hal_srng_set_flush_last_ts(hal_srng);
+		qdf_atomic_set(&soc->tx_pending_rtpm, 0);
 		dp_debug("flushed");
 	}
 }