input: touchscreen: st: set device pm state

Keep device to be awake when "aoi_wake_on_suspend" is enabled. This flag is
disabled by default, so it will not impact normal scenes.

Change-Id: I6cc35191d7c4ff7bda2cd2f5d355eacbee49b09a
Signed-off-by: Fei Mao <feim1@codeaurora.org>