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

Conflicts:

	libgralloc/framebuffer.cpp
	libgralloc/gpu.cpp

Conflicts:

	common.mk
	libgralloc/Android.mk
	libgralloc/gpu.cpp
	libgralloc/gralloc_priv.h
	libgralloc/mapper.cpp
	libhwcomposer/Android.mk