drivers:i2c: Modify I2C driver for Exynos4

This patch modifies the S3C i2c driver to support both Exynos4 and Exynos5

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>