media: em28xx: fix memory leak in em28xx_init_dev

In the em28xx_init_rev, if em28xx_audio_setup fails, this function fails
to deallocate the media_dev allocated in the em28xx_media_device_init.

Fix this by adding em28xx_unregister_media_device to free media_dev.

BTW, this patch is tested in my local syzkaller instance, and it can
prevent the memory leak from occurring again.

CC: Pavel Skripkin <[e-mail]>
Fixes: 37ecc7b1278f ("[media] em28xx: add media controller support")
Signed-off-by: Dongliang Mu <[e-mail]>
Reported-by: syzkaller <[e-mail]>
Signed-off-by: Hans Verkuil <[e-mail]>
Signed-off-by: Mauro Carvalho Chehab <[e-mail]>

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

···
 
 	if (dev->is_audio_only) {
 		retval = em28xx_audio_setup(dev);
-		if (retval)
-			return -ENODEV;
+		if (retval) {
+			retval = -ENODEV;
+			goto err_deinit_media;
+		}
 		em28xx_init_extension(dev);
 
 		return 0;
···
 		dev_err(&dev->intf->dev,
 			"%s: em28xx_i2c_register bus 0 - error [%d]!\n",
 		       __func__, retval);
-		return retval;
+		goto err_deinit_media;
 	}
 
 	/* register i2c bus 1 */
···
 				"%s: em28xx_i2c_register bus 1 - error [%d]!\n",
 				__func__, retval);
 
-			em28xx_i2c_unregister(dev, 0);
-
-			return retval;
+			goto err_unreg_i2c;
 		}
 	}
 
···
 	em28xx_card_setup(dev);
 
 	return 0;
+
+err_unreg_i2c:
+	em28xx_i2c_unregister(dev, 0);
+err_deinit_media:
+	em28xx_unregister_media_device(dev);
+	return retval;
 }
 
 static int em28xx_duplicate_dev(struct em28xx *dev)