[media] em28xx-video: do not unregister the v4l2 dummy clock before v4l2_device_unregister() has been called

Otherwiese the core refuses to unregister the clock and the following warning
appears in the system log:

"WARNING: ... at drivers/media/v4l2-core/v4l2-clk.c:231 v4l2_clk_unregister+0x8a/0x90 [videodev]()
 v4l2_clk_unregister(): Refusing to unregister ref-counted 11-0030:mclk clock!"

Signed-off-by: Frank Schäfer <fschaefer.oss@googlemail.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>

drivers/media/usb/em28xx/em28xx-video.c

@@ -1918,14 +1918,14 @@ static int em28xx_v4l2_fini(struct em28xx *dev)
 		video_unregister_device(dev->vdev);
 	}
 
+	v4l2_ctrl_handler_free(&dev->ctrl_handler);
+	v4l2_device_unregister(&dev->v4l2_dev);
+
 	if (dev->clk) {
 		v4l2_clk_unregister_fixed(dev->clk);
 		dev->clk = NULL;
 	}
 
-	v4l2_ctrl_handler_free(&dev->ctrl_handler);
-	v4l2_device_unregister(&dev->v4l2_dev);
-
 	if (dev->users)
 		em28xx_warn("Device is open ! Memory deallocation is deferred on last close.\n");
 	mutex_unlock(&dev->lock);