i2c: davinci: add OF support

add of support for the davinci i2c driver.

Signed-off-by: Heiko Schocher <hs@denx.de>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>

[wsa: fix indentation in the binding description]

Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>