cros_ec: power: Add a tunnelled version of the tps65090 driver

cros_ec: power: Add a tunnelled version of the tps65090 driver

Unfortunately on Pit the AP has no direct access to the tps65090 but must
talk through the EC (over SPI) to the EC's I2C bus.

When driver model supports PMICs this will be relatively easy. In the
meantime the best approach is to duplicate the driver. It will be refactored
once driver model support is expanded.

Signed-off-by: Simon Glass <[email protected]>
Tested-by: Ajay Kumar <[email protected]>
Signed-off-by: Minkyu Kang <[email protected]>