qcacmn: Don't return if mon vap down in dp_rx_mon_dest_process

If mon vap is down, pdev->monitor_vdev will be set to NULL.
Then function returns, this return will causing mon dest ring not reaped,
causing mon dest ring full FW assert.
And it'll causing mon status ring & dest ring out of sync.

Change-Id: Ie10792da2a4a78d959c676c4b4fba3d9ee05c6e6

dp/wifi3.0/dp_rx_mon_dest.c

@@ -844,10 +844,6 @@ void dp_rx_mon_dest_process(struct dp_soc *soc, uint32_t mac_id, uint32_t quota)
 	qdf_assert(hal_soc);
 
 	qdf_spin_lock_bh(&pdev->mon_lock);
-	if (pdev->monitor_vdev == NULL) {
-		qdf_spin_unlock(&pdev->mon_lock);
-		return;
-	}
 
 	if (qdf_unlikely(hal_srng_access_start(hal_soc, mon_dst_srng))) {
 		QDF_TRACE(QDF_MODULE_ID_TXRX, QDF_TRACE_LEVEL_ERROR,