hwc: Add setting to disable idleinvalidator

Added the ability to disable idleInvalidator when the
debug.mdpcomp.idletime property is set to "-1". The hwc test app
displays image on the screen with surface flinger turned off.
This causes timeout, so this change is to allow the testapp to
disable the timeout functionality by setting property.

Change-Id: I1adf28eea33ea73f3695644bec95056d16bd85f8
1 file changed