drm/tegra: sor: Demidlayer

Implement encoder and connector within the eDP driver itself using the
Tegra output helpers rather than using the Tegra output as midlayer. By
doing so one level of indirection is removed and output drivers become
more flexible while keeping the majority of the advantages provided by
the common output helpers.

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