qcacmn: Change log level for Special vap channel change

During special vap channel change, we see "monitor vap already created"
print on the console. This is the expected print, because
pdev->monitor_configured is set during wifi up. Therefore, change the
debug level of this print from ERROR to DEBUG.

Change-Id: Ia290b74d9be20691eac3ebc50f6cc3fff3e94953
CRs-Fixed: 2529580

dp/wifi3.0/dp_main.c

@@ -6339,9 +6339,8 @@ static QDF_STATUS dp_vdev_set_monitor_mode(struct cdp_vdev *vdev_handle,
 
 	/*Check if current pdev's monitor_vdev exists */
 	if (pdev->monitor_configured) {
-		QDF_TRACE(QDF_MODULE_ID_TXRX, QDF_TRACE_LEVEL_ERROR,
+		QDF_TRACE(QDF_MODULE_ID_TXRX, QDF_TRACE_LEVEL_DEBUG,
 			  "monitor vap already created vdev=%pK\n", vdev);
-		qdf_assert(vdev);
 		return QDF_STATUS_E_RESOURCES;
 	}