hwc: support vsync notification via sysfs

Change-Id: Ie2172b5fb2e8595136f6ccb28abd9f8ce89a526f
hwc: fix timing issue with vsync sysfs loop

Change-Id: I6e0307e0fd5ea84748ddb580062b21f697512603
omap4xxx: add flag to allow custom libion

Due to kernel changes I need to stop the omap4xxx/libion via
BOARD_USES_CUSTOM_LIBION flag and instead use a custom libion
in my device trees.

Change-Id: Ic48e8c51456c76dfd9bca00cb59581deb2cfc510
Signed-off-by: Hashcode <hashcode0f@gmail.com>