media: dvbdev: drop refcount on error path in dvb_device_open()

[ Upstream commit a2dd235df435a05d389240be748909ada91201d2 ]

If call to file->f_op->open() fails, then call dvb_device_put(dvbdev).

Fixes: 0fc044b2b5e2 ("media: dvbdev: adopts refcnt to avoid UAF")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Sasha Levin <sashal@kernel.org>