rk_i2c: Add driver for the I2C controller present in RockChip SoC

This controller have a special mode for RX to help with smbus-like transfer
when the controller will automatically send the slave address, register address
and read the data. Use it when possible.
The same mode for TX is describe is the datasheet but is broken and have been
since ~10 years of presence of this controller in RockChip SoCs.

Attach this driver early at we need it to communicate with the PMIC early in the
boot.
Do not hook it to the kernel build for now.