Fake VSYNC events

*1,Hack for devices without proper working VSYNC, so they
are able to use composer version

Change-Id: I748959cac936985a78ef864a97adb82eacffd606

*2,hwcomposer: disable vsync based on board preference

follow only the board preference instead of checking both platform and
board preference

Conflicts:
	libhwcomposer/hwc.cpp
	libhwcomposer/hwc_vsync.cpp