input: touchscreen: Handle suspend event in focaltech driver

Add VSYNC_SUSPEND as a touch suspend event.
This event is generated when display is dimmed.
Touch can be suspended on this event.

Change-Id: I548dd2efc2a4545cffa98bc1f20549b23cb558bf
Signed-off-by: Venkata Prahlad Valluru <vvalluru@codeaurora.org>