drm/tegra: sor: Hook up I2C-over-AUX to output

This is necessary for the output abstraction to retrieve a list of valid
modes from the EDID of a connected panel/monitor. This will be useful in
conjunction with DisplayPort support that will be added in a subsequent
patch, so that the driver can read EDID via the AUX channel.

Signed-off-by: Thierry Reding <treding@nvidia.com>