drm/tegra: hdmi - Fix disable sequence

For some reason when the PW*_ENABLE and PM*_ENABLE fields are cleared
during disable, the HDMI output stops working properly. Resetting and
initializing doesn't help.

Comment out those accesses for now until it has been determined what to
do about them.

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