drm/msm/dpu: clean up destination scaler residue

Destination scaling(DS) is a Snapdragon hardware feature to
scale up the display ROI after layer blending. DPU driver doesn't
support programming of DS blocks yet. This change cleans up the
residual code present in catalog and RM for DS block handling.
Support for the same can be added back when the feature is
formally implemented.

changes in v5:
	- introduced in the series

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