[media] zd1301_demod: ZyDAS ZD1301 DVB-T demodulator driver

ZyDAS ZD1301 is chip having USB interface and DVB-T demodulator
integrated. This driver is for demodulator part.
Driver is very reduced, just basic demodulator functionality, no
statistics at all. It registers as a platform driver to driver core.

Signed-off-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>