i2c-eg20t: add driver for Intel EG20T

I2C driver for Intel EG20T PCH

Signed-off-by: Tomoya MORINAGA <tomoya-linux@dsn.okisemi.com>
Reviewed-by: Linus Walleij <linus.walleij@stericsson.com>
Signed-off-by: Qi Wang <qi.wang@intel.com>
[ben-linux@fluff.org: reworded commit message]
Signed-off-by: Ben Dooks <ben-linux@fluff.org>