rockchip: i2c: Enable i2c for rk3399

To enable mipi display, we need to enable pmic
rk808 first for lcd3v3 power,which use i2c0 to
communicate with soc. So enable i2c0.

Signed-off-by: Eric Gao <eric.gao@rock-chips.com>
Acked-by: Simon Glass <sjg@chromium.org>