drm/msm: clean up debugfs nodes in msm and msm/sde

This change removes unused debugfs nodes from msm/sde. It also
changes some permissions of nodes that no longer need both
read and write access to read only.

Change-Id: Ib89dd5c81f0c8b51cdcbfb92a9ac3affbaf2183c
Signed-off-by: Samantha Tran <samtran@codeaurora.org>