display: Remove genlock usage

genlock is no-op from Android 4.2 onwards since the sync framework
is used for explicit synchronization.

Change-Id: Idd1df589516534a683e0fa1ef0cfbb7f0e411f67
Merge branch 'cm-10.1' of https://github.com/CyanogenMod/android_hardware_qcom_display-caf into jb-mr1