touch: synaptics: Ignore palm detect while in ambient

When a device is in ambient mode, a palm detect event should be ignored
and the device should not wake up due to this.

if the driver reports any event to userspace, the userspace would be
able to use the event for wakeup

Change-Id: Ia6c96fb456fb66a965996fab0331b78b17690f61
Signed-off-by: Devin Kim <dojip.kim@lge.com>