V4L/DVB (6812): media: video: usbvision: remove ctrlUrbLock

The ctrlUrbLock has all it's users commented out, and so it's unused.  This
patch removes it.

Signed-off-by: Daniel Walker <dwalker@mvista.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thierry MERLE <thierry.merle@free.fr>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>