FDT: Add compatible string for I2C

Add required compatible information for I2C driver.

Signed-off-by: Rajeshwari Shinde <rajeshwari.s@samsung.com>
Acked-by: Simon Glass <sjg@chromium.org>
Acked-by: Heiko Schocher <hs@denx.de>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>