tegra: fdt: i2c: Add extra I2C bindings for U-Boot

Add U-Boot's peripheral clock information to the Tegra20 device tree file.

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