rx6110sa: Add possibility to use both I2C and SMBus for the RTC

The driver for the RTC RX6110SA is designed to be used with I2C bus.
This patch adds the possibility to use SMBus operations to access the
RTC. For this purpose the Kconfig switch RX6110SA_USE_SMBUS is added. It
is not enabled per default so that I2C will be used. One can set this
switch on board level to use SMBus instead.

Change-Id: I4827ae2c544e8002399d94a1159acacd8176c5e9
Signed-off-by: Werner Zeh <werner.zeh@siemens.com>
Reviewed-on: https://review.coreboot.org/19978
Reviewed-by: Aaron Durbin <adurbin@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
2 files changed