v4l: reorganize RF tuner control ID numbers

It appears that controls are ordered by ID number. Change order of
controls by reorganizing assigned IDs now as we can. It is not
reasonable possible after the API is released. Leave some spare
space between IDs too for future extensions.

Cc: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Antti Palosaari <crope@iki.fi>
DocBook: document RF tuner bandwidth controls

Add documentation for RF tuner bandwidth controls. These controls are
used to set filters on tuner signal path.

Cc: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Antti Palosaari <crope@iki.fi>