input: touchscreen: st: add touch notification when suspend

When tap or swipe in a dedicated region, tp driver will notify
the subsystem/driver who has registered.
And this feature is not enabled by default; write the sysfs node
to enable it by demand.

Change-Id: Ie6312e8a0680b0abb9fed9a647bc9cee36985286
Signed-off-by: Rick Huang <rhuang@codeaurora.org>
Signed-off-by: Fei Mao <feim1@codeaurora.org>