ARM: S5PV210: add common I2C device helpers

This patch adds I2C platform helpers required by s3c2440-i2c driver.

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