V4L/DVB (13478): cx18: remove bogus init call.

The cx18 av core implemented an init call for no good reason. It's now
turned into an internal function.

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Reviewed-by: Andy Walls <awalls@radix.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>