exynos:pinmux: Add pinmux support for i2c

This patch add pinmux for I2C for Exynos4

Signed-off-by: Piotr Wilczek <p.wilczek@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
CC: Minkyu Kang <mk7.kang@samsung.com>