V4L/DVB: cx2341x: convert to the control framework

Since this module is also used by drivers that are not yet converted, the old
and new code have to co-exist.

The source is split into three parts: a common part at the top, which is used
by both old and new code, then the old code followed by the new control
framework implementation. This new code is much more readable (and shorter!)
than the original code.

Once all bridge drivers that use this are converted the old code can be
deleted.

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>