* Read sysfs entries, to get vsync timestamp from kernel.
* External display continues to use in ueventThread.
* A new thread, vsyncThread is created to read and send vsync
timestamps to HAL.
* Disable H/W VSYNC for MDP 5.x targets until kernel changes are
complete.
(cherry picked from commit a61a58cb775631cd3899211f6ff0aed232f5f3c0)
Change-Id: I58e09a092f81d4ff78b8cb4072ff06d2500c6f53