[media] v4l: add new tuner types for SDR

Define tuner types V4L2_TUNER_ADC and V4L2_TUNER_RF for SDR usage.

ADC is used for setting sampling rate (sampling frequency) to SDR
device.

Another tuner type, named as V4L2_TUNER_RF, is possible RF tuner.
Is is used to down-convert RF frequency to range ADC could sample.
Having RF tuner is optional, whilst in practice it is almost always
there.

Also add checks to VIDIOC_G_FREQUENCY, VIDIOC_S_FREQUENCY and
VIDIOC_ENUM_FREQ_BANDS only allow these two tuner types when device
type is SDR (VFL_TYPE_SDR). For VIDIOC_G_FREQUENCY we do not check
tuner type, instead override type with V4L2_TUNER_ADC in every
case (requested by Hans in order to keep functionality in line with
existing tuners and existing API does not specify it).

Prohibit VIDIOC_S_HW_FREQ_SEEK explicitly when device type is SDR,
as device cannot do hardware seek without a hardware demodulator.

Signed-off-by: Antti Palosaari <crope@iki.fi>
Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>

include/uapi/linux/videodev2.h

@@ -159,6 +159,8 @@ enum v4l2_tuner_type {
 	V4L2_TUNER_RADIO	     = 1,
 	V4L2_TUNER_ANALOG_TV	     = 2,
 	V4L2_TUNER_DIGITAL_TV	     = 3,
+	V4L2_TUNER_ADC               = 4,
+	V4L2_TUNER_RF                = 5,
 };
 
 enum v4l2_memory {