i2c: cbus-gpio: Switch to use GPIO descriptors

This augments the CBUS GPIO I2C driver to use GPIO
descriptors for clock, sel and data. We drop the platform
data that was only used for carrying GPIO numbers and
use machine descriptor tables instead.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Tested-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>