[SPARC] Videopix Frame Grabber: Fix unreleased lock in vfc_debug()

Videopix Frame Grabber: vfc_debug() doesn't release the device lock
when copy_from_user() fails

Signed-off-by: Matthias Kaehlcke <matthias.kaehlcke@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>