[media] tm6000: Warning cleanup

drivers/media/video/tm6000/tm6000-video.c: In function ‘tm6000_release’:
drivers/media/video/tm6000/tm6000-video.c:1608:7: warning: unused variable ‘err’ [-Wunused-variable]

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>