ARM: S3C2416: Add platform helpers for setup SDHCI

Samsung S3C2416 has two SDHCI controllers compatible with other
Samsung's SoCs (S3C64XX, S5PC100 etc...).

Add required platform setup code that the devices can be used with
sdhci-s3c driver.

Signed-off-by: Yauhen Kharuzhy <yauhen.kharuzhy@promwad.com>
[kgene.kim@samsung.com: change to __raw_{readl,writel} from {readl,writel}]
[kgene.kim@samsung.com: build error fixes]
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>