tegra: i2c: Add I2C driver

Add basic i2c driver for Tegra2 with 8- and 16-bit address support.
The driver requires CONFIG_OF_CONTROL to obtain its configuration
from the device tree.

(Simon Glass: sjg@chromium.org modified for upstream)

Signed-off-by: Simon Glass <sjg@chromium.org>
Acked-by: Heiko Schocher <hs@denx.de>
Acked-by: Stephen Warren <swarren@wwwdotorg.org>
Signed-off-by: Tom Warren <twarren@nvidia.com>