V4L/DVB (4838): Fix cx88-blackbird null pointer

Allows 'debug=1' for cx88-blackbird module (dev needs to be valid for
dprintk). Fixes a null-pointer dereference when using debug=1.
Signed-off-by: NJelle Foks <jelle@foks.8m.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@infradead.org>

drivers/media/video/cx88/cx88-blackbird.c

@@ -942,9 +942,10 @@ static int mpeg_open(struct inode *inode, struct file *file)
 	struct cx8802_driver *drv = NULL;
 	int err;
 
+       dev = cx8802_get_device(inode);
+
 	dprintk( 1, "%s\n", __FUNCTION__);
 
-	dev = cx8802_get_device(inode);
 	if (dev == NULL)
 		return -ENODEV;