V4L/DVB: cx25840: Fix typo in volume control initialization: 65335 vs. 65535

The wrong value for the volume control limit, 65335 vs. 65535,
prevents proper cx25840 v4l2_subdevice initialization.

Reported-by: Igor M. liplianin <liplianin@me.by>
Signed-off-by: Andy Walls <awalls@md.metrocast.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>