msm: mdss: Hold MDP clock Ref count in pan_display path

If handoff fails, the clock ref count becomes 0 and iommu
will get detached. In pan display path, since at that
particular instant iommu gets detached, we use physical
address. After this if iommu is again attached and physical
address is fetched, it can result in continuous IOMMU page
faults. To address this hold MDP clock ref count
in pan display path.

Change-Id: I2370b276acdced2cf22083eb80fcad1b2e454315
Signed-off-by: Jayant Shekhar <jshekhar@codeaurora.org>
msm: mdss: Add update notify for backlight change in static screen

Previously, the change of backlight sysfs node value will not trigger
notify updates if display is in static screen case. This will cause
delay or wrong configuration for assertive display. This patch fixes
the above issue by adding an update notify if backlight changes when
there are no display updates.

Change-Id: I1475896214a50dc1fa71739aa751b2e626d27adb
Signed-off-by: Ping Li <quicpingli@codeaurora.org>