media: dvbdev: remove double-unlock

[ Upstream commit 122d0e8dd050cc5dc3fb9e9b5f2dee3c5276ce35 ]

As warned by smatch:
	drivers/media/dvb-core/dvbdev.c: drivers/media/dvb-core/dvbdev.c:529 dvb_register_device() error: double unlock 'sem:&minor_rwsem'

Reported-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Stable-dep-of: 8c64f4cdf4e6 ("media: edia: dvbdev: fix a use-after-free")
Signed-off-by: Sasha Levin <sashal@kernel.org>