board: samsung: e850-96: Add PMIC code

board: samsung: e850-96: Add PMIC code

Add functions for configuring voltage regulators on S2MPU12 PMIC chip
for E850-96 board. The chip is accessed by commanding APM core (via
ACPM IPC protocol) to perform corresponding transfers over I3C bus.

The most important regulator being set up is LDO24 used for LAN9514 chip
power. As LAN9514 implements USB hub and Ethernet controller
functionality, it's crucial to enable and configure LDO24 to be able to
use it further. While at it, configure the rest of regulators that might
be needed later, both in the bootloader and in kernel.

Signed-off-by: Sam Protsenko <semen.protsenko@linaro.org>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>