Fall back to single plane composition in Idle case.

Fall back to single plane composition in Idle case.

There is no need to continue using different planes for composition
in case the system is not really updating any new content. We now
track this and if we haven't updated content for the previous three
vblanks, we fall back to single plane composition for the current
content on screen.

Jira: None.
Test: Power consumption is minimum in idle case scenarious.
Signed-off-by: Kalyan Kondapally <kalyan.kondapally@intel.com>