drm/msm/sde: trigger connector pre commit during disables

Trigger a final pre-commit callback on DSI connectors during
disable call flows. This allows for any final cleanup operations
to be performed.

Change-Id: I49a280bf7d31d75f91087e9631c36f1847f1ff10
Signed-off-by: Clarence Ip <cip@codeaurora.org>