tegra: Avoid using I2C prior to relocation

Tegra recently moved to the new I2C framework, which sets up I2C prior to
relocation, and prior to calling i2c_init_board(). This causes a crash on
Tegra boards.

Tested-by: Stephen Warren <swarren@nvidia.com>
Signed-off-by: Simon Glass <sjg@chromium.org>