ARM: tegra: Enable eDP for Venice2

Venice2 has a 12.9" (2560x1700) panel connected to the eDP output of the
Tegra124. The panel has an EDID to describe the video timings but needs
a few extra nodes to get the backlight to come up.

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