media: cedrus: Fix missing cleanup in error path

According to the documentation struct v4l2_fh has to be cleaned up with
v4l2_fh_exit() before being freed. [1]
Currently there is no actual bug here, when v4l2_fh_exit() isn't called.
v4l2_fh_exit() in this case only destroys internal mutex. But it may
change in the future, when v4l2_fh_init/v4l2_fh_exit will be enhanced.

1. https://docs.kernel.org/driver-api/media/v4l2-fh.html

Signed-off-by: Samuel Holland <samuel@sholland.org>
Signed-off-by: Andrey Skvortsov <andrej.skvortzov@gmail.com>
Fixes: 50e761516f ("media: platform: Add Cedrus VPU decoder driver")
Cc: stable@vger.kernel.org
Acked-by: Paul Kocialkowski <paulk@sys-base.io>
Signed-off-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>

drivers/staging/media/sunxi/cedrus/cedrus.c

@@ -391,6 +391,7 @@ static int cedrus_open(struct file *file)
 err_m2m_release:
 	v4l2_m2m_ctx_release(ctx->fh.m2m_ctx);
 err_free:
+	v4l2_fh_exit(&ctx->fh);
 	kfree(ctx);
 	mutex_unlock(&dev->dev_mutex);