drm/tegra: sor: Unify eDP and DP support

The SOR0 on Tegra210 does, contrary to what was previously assumed, in
fact support DisplayPort. The difference between SOR0 and SOR1 is that
the latter supports audio and HDCP over DP, whereas the former doesn't.

The code for eDP and DP is now almost identical and the differences can
easily be parameterized based on the presence of a panel. There is no
need any longer to duplicate the code.

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