qcacmn: Reset filters for buffer ring when deleting monitor mode

Currently, when monitor interface is going down, buffer ring filters
are not being reset.
To fix this, set mv_dev to NULL after filter reset.

Change-Id: I7555acd6b4a54a362e36a43a970ab1c75e3c24c8
CRs-Fixed: 3841235

dp/wifi3.0/monitor/dp_mon.c

@@ -261,8 +261,6 @@ QDF_STATUS dp_reset_monitor_mode_unlock(struct cdp_soc_t *soc_hdl,
 #endif
 	}
 
-	mon_pdev->mvdev = NULL;
-
 	/*
 	 * Lite monitor mode, smart monitor mode and monitor
 	 * mode uses this APIs to filter reset and mode disable
@@ -293,6 +291,7 @@ QDF_STATUS dp_reset_monitor_mode_unlock(struct cdp_soc_t *soc_hdl,
 				   soc);
 	}
 
+	mon_pdev->mvdev = NULL;
 	mon_pdev->monitor_configured = false;
 
 	return QDF_STATUS_SUCCESS;