[media] em28xx: Only deallocate struct em28xx after finishing all extensions

We can't free struct em28xx while one of the extensions is still
using it.

So, add a kref() to control it, freeing it only after the
extensions fini calls.

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

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

@@ -676,6 +676,8 @@ static int em28xx_ir_init(struct em28xx *dev)
 		return 0;
 	}
 
+	kref_get(&dev->ref);
+
 	if (dev->board.buttons)
 		em28xx_init_buttons(dev);
 
@@ -816,7 +818,7 @@ static int em28xx_ir_fini(struct em28xx *dev)
 
 	/* skip detach on non attached boards */
 	if (!ir)
-		return 0;
+		goto ref_put;
 
 	if (ir->rc)
 		rc_unregister_device(ir->rc);
@@ -824,6 +826,10 @@ static int em28xx_ir_fini(struct em28xx *dev)
 	/* done */
 	kfree(ir);
 	dev->ir = NULL;
+
+ref_put:
+	kref_put(&dev->ref, em28xx_free_device);
+
 	return 0;
 }