tegra: video: Add Embedded DisplayPort driver

This interface is used on laptop devices based on Tegra. Add a driver which
provides access to the eDP interface. The driver uses the display port
uclass.

Signed-off-by: Simon Glass <sjg@chromium.org>
Acked-by: Anatolij Gustschin <agust@denx.de>
Signed-off-by: Tom Warren <twarren@nvidia.com>