ARM: S5PC1xx: add platform helpers for i2c adapter devices

Samsung S5PC100 has I2C bus controller compatible with the one known from
previous SoCs series. Add required platform setup and support code that
it can be used with s3c2410-i2c driver.

Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Ben Dooks <ben-linux@fluff.org>