remove stub rk i2c driver
i2c: add driver for Rockchip RK3xxx SoCs integrated I2C adapter

Adds a driver for the native I2C adapter found in Rockchip RK3xxx SoCs.

Signed-off-by: Max Schwarz <max.schwarz@online.de>
dts: use rocchip hardware i2c IP
adapt rk3x-i2c to new grf structure and move some probe stuff around
to make the failure path easier