ARM: S5PV210: Add Support for MMC regulators on GONI board

Add required platform definitions for MMC power regulators on Samsung
Goni board. GPIO pin GONI_EXT_FLASH_EN has been transferred from machine
startup code to fixed voltage regulator.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Reviewed-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>