drivers/i2c: Add new driver for RTC type PCF8523

This driver enables the usage of an external RTC chip PCF8523 which is
connected to the I2C bus. The I2C address of this device is fixed.
One can change parameters in device tree so that the used setup can be
adapted in device tree to match the configuration of the device on the
mainboard.

Change-Id: I2d7e161c9e12b720ec4925f1acfd1dd8ee6ee5f5
Signed-off-by: Werner Zeh <werner.zeh@siemens.com>
Reviewed-on: https://review.coreboot.org/15641
Tested-by: build bot (Jenkins)
Reviewed-by: Kyösti Mälkki <kyosti.malkki@gmail.com>
5 files changed