Allow px4io detect to be run when IO is already running

src/drivers/px4io/px4io.cpp

@@ -487,7 +487,7 @@ PX4IO::detect()
 {
 	int ret;
 
-	ASSERT(_task == -1);
+	if (_task == -1) {
 
 		/* do regular cdev init */
 		ret = CDev::init();
@@ -506,6 +506,8 @@ PX4IO::detect()
 			
 			return -1;
 		}
+	}
+
 	log("IO found");
 
 	return 0;