drm/msm: avoid sde rsc debug mode access during idle pc

SDE driver removes AHB vote during idle pc and it triggers
cnoc disconnect. Any SDE RSC register access in this state
may lead to noc error and causes panic. This patch avoids
sde rsc debug node access during idle pc.

Change-Id: I3426cfecc47c36a509cf3621937ae172991bd4dd
Signed-off-by: Dhaval Patel <pdhaval@codeaurora.org>