soc: samsung: Add Exynos Adaptive Supply Voltage (ASV) driver

soc: samsung: Add Exynos Adaptive Supply Voltage (ASV) driver

The purpose of exynos-asv driver added in this patch is to modify
CPU OPPs as defined in DT depending on exact SoC revision specified
by data available in the CHIP ID block.

This patch is based on hardkernel code:
https://github.com/hardkernel/linux/blob/odroidxu4-4.14.y/arch/arm/mach-exynos/exynos5422-asv.c
https://github.com/hardkernel/linux/blob/odroidxu4-4.14.y/arch/arm/mach-exynos/exynos5422-asv.h

Change-Id: I115c693684ed5e87d69d82f662a1a828ad1c998a
Signed-off by: Sylwester Nawrocki <s.nawrocki@samsung.com>