hwc: Increase idle timeout value to 600

Increasing idle timeout value to 600 to avoid
frequent wakeups of GPU and swithces
between GPU and MDP leading to flicker issues.

Change-Id: I27780ca40caa01e1ae0d5f10334d91cbe2329b45
hwc: Fix  PTOR for overlapping PTOR regions.

If two PTOR layers are overlapping, remove overlapping
region from bottom PTOR layer if possible to reduce total
overlapping layers in a region.

Change-Id: I695c097360ac5a8fa123e014f21380169519eb32