Add initial support for Dual-DVB-T stick based on DiB7700 and MT2266

- Microtune MT2266 driver.
- Preliminary support for these dual tuner devices :
  - Pinnacle Dual DVB-T diversity
  - Terratec Cinergy DT USB XS diversity
  - Hauppauge Nova TD USB
Signed-off-by: NOlivier DANET <odanet@caramail.com>
Signed-off-by: NPatrick Boettcher <pb@linuxtv.org>
Signed-off-by: NMauro Carvalho Chehab <mchehab@infradead.org>