arm: mvebu: helios4: Enable I2C and IO Expander

Enable Marvell I2C driver and I2C IO expander. Set default bus to
external I2C bus. Define I2C aliases in device tree so it can be
recognized by the driver.

Signed-off-by: Aditya Prayoga <aditya@kobol.io>
Reviewed-by: Stefan Roese <sr@denx.de>
Tested-By: Dennis Gilmore <dgilmore@redhat.com>
Reviewed-By: Dennis Gilmore <dgilmore@redhat.com>
Signed-off-by: Stefan Roese <sr@denx.de>