[DFS] "console" device check.

[DFS] To make sure the "console" device exist or not when initialize
console device.

components/dfs/filesystems/devfs/console.c

@@ -78,6 +78,9 @@ void rt_console_init(const char* device_name)
 	rt_device_t device;
 	/* register to device framework */
 
+	device = rt_device_find("console");
+	if (device) return; /* not register a same name device */
+
 	device = rt_device_find(device_name);
 	if (device != RT_NULL)
 	{