msi001: Mirics MSi001 silicon tuner driver

That RF tuner driver is bound via SPI bus model and it implements V4L
subdev API. I split it out from MSi3101 SDR driver.
MSi3101 = MSi2500 + MSi001.

Signed-off-by: Antti Palosaari <crope@iki.fi>
msi3101: use msi001 tuner driver

Remove MSi001 RF tuner related code as MSi001 functionality is moved
to own driver.

Implement SPI master adapter.

Attach MSi001 driver via SPI / V4L subdev framework.

Signed-off-by: Antti Palosaari <crope@iki.fi>
MAINTAINERS: add msi001 driver

Mirics MSi001 silicon tuner driver. Currently in staging as SDR API
is not ready.

Signed-off-by: Antti Palosaari <crope@iki.fi>
MAINTAINERS: add msi3101 driver

Mirics MSi2500 (MSi3101) SDR ADC + USB interface driver. Currently
in staging as SDR API is not ready.

Signed-off-by: Antti Palosaari <crope@iki.fi>
MAINTAINERS: add rtl2832_sdr driver

Realtek RTL2832 SDR driver. Currently in staging as SDR API is not
ready.

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