disp: msm: sde: fix system cache feature enable

In current driver if client did not reset system cache
crtc property, system cache write state is on forever and
breaks the system cache feature. This change restricts
entering into cache write state only if it's commit right
after idle notify. This change also adds event logs to
capture system cache feature state changes.

Change-Id: Ie46fc9113f752ed8989dab99301690a13003b00b
Signed-off-by: Prabhanjan Kandula <pkandula@codeaurora.org>