drm/tegra: Add new UAPI to header

Update the tegra_drm.h UAPI header, adding the new proposed UAPI.
The old staging UAPI is left in for now, with minor modification
to avoid name collisions.

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