drm/msm/sde: make sure all locks are acquired during lastclose

Ensure that we actually acquired all locks before proceeding to
disable modes and revert custom properties back to their default
values.  This patch adds the typical grab locks and backoff dance
to avoid lock contention.

Change-Id: Iaaea9fd75a79be8978d048f93d61ea0f7d4f8a4d
Signed-off-by: Steve Cohen <cohens@codeaurora.org>