tuner-core.c improvments and Ymec Tvision TVF8533MF support

tuner-core.c, tuner.h:

- tuner-core changed to support multiple I2C devices used on
some adapters;
- Kconfig now has an option (CONFIG_TUNER_MULTI_I2C) to enable
this new behavor;
- By default, even enabling CONFIG_TUNER_MULTI_I2C, tuner-core
emulates the old behavor, using first I2C device for both FM and TV;
- There is a new i2c command (TUNER_SET_ADDR) to allow tuner
clients to select I2C address for FM or TV tuner;
- Tuner I2C dettach now generates a warning on syslog if failed.

tuner-simple.c:
- TVision TVF-8531MF and TVF-5533 MF tuner included. It uses, by
default, I2C on 0xC2 address for TV and on 0xC0 for Radio. Both TV and FM Radio mode are working.