DocBook: document RF tuner gain controls

Add documentation for LNA, mixer and IF gain controls. These
controls are RF tuner specific.

Cc: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Antti Palosaari <crope@iki.fi>
Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
DocBook: V4L: add V4L2_SDR_FMT_CU8 - 'CU08'

Document V4L2_SDR_FMT_CU8 SDR format.
It is complex unsigned 8-bit IQ sample. Used by software defined
radio devices.

Cc: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Antti Palosaari <crope@iki.fi>
Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
DocBook: V4L: add V4L2_SDR_FMT_CU16LE - 'CU16'

Document V4L2_SDR_FMT_CU16LE format.
It is complex unsigned 16-bit little endian IQ sample. Used by
software defined radio devices.

Cc: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Antti Palosaari <crope@iki.fi>
Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
DocBook: media: document V4L2_CTRL_CLASS_RF_TUNER

It is class for RF tuner specific controls, like gain controls,
filters, signal strength.

Cc: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Antti Palosaari <crope@iki.fi>
xc2028: silence compiler warnings

There is now new tuner types which are not handled on that switch-case.
Print error if unknown tuner type is meet.

drivers/media/tuners/tuner-xc2028.c: In function ‘generic_set_freq’:
drivers/media/tuners/tuner-xc2028.c:1037:2: warning: enumeration value ‘V4L2_TUNER_ADC’ not handled in switch [-Wswitch]
  switch (new_type) {
  ^
drivers/media/tuners/tuner-xc2028.c:1037:2: warning: enumeration value ‘V4L2_TUNER_RF’ not handled in switch [-Wswitch]

Cc: Mauro Carvalho Chehab <m.chehab@samsung.com>
Signed-off-by: Antti Palosaari <crope@iki.fi>
v4l: add RF tuner channel bandwidth control

Modern silicon RF tuners has one or more adjustable filters on
signal path, in order to filter noise from desired radio channel.

Add channel bandwidth control to tell the driver which is radio
channel width we want receive. Filters could be then adjusted by
the driver or hardware, using RF frequency and channel bandwidth
as a base of filter calculations.

On automatic mode (normal mode), bandwidth is calculated from sampling
rate or tuning info got from userspace. That new control gives
possibility to set manual mode and let user have more control for
filters.

Cc: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Antti Palosaari <crope@iki.fi>
msi3101: implement tuner bandwidth control

Implement control that user could adjust tuner filters manually,
if he wish.

Signed-off-by: Antti Palosaari <crope@iki.fi>
rtl2832_sdr: implement tuner bandwidth control

Implement control that user could adjust tuner filters manually,
if he wish.

Signed-off-by: Antti Palosaari <crope@iki.fi>