ARM: S5PV210: Add MAX8998 PMIC support for GONI

This patch adds required platform definitions for MAX8998 PMIC driver. Power
regulators for LDO and BUCK outputs has been defined as well as a simple
gpio-keys button for power key (to enable wakeup functionality with
external interrupt).

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
[broonie@opensource.wolfsonmicro.com: For the regulator API usage]
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
[kgene.kim@samsung.com: minor title fix]
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>