drm/msm/dpu: remove stale display port programming

Remove stale display port programming. It can be
added back with DPU support for display port.

Signed-off-by: Jeykumar Sankaran <jsanka@codeaurora.org>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Rob Clark <robdclark@gmail.com>