qbt_handler: Change return type of qbt_poll

Add changes to make touch events notifier static.
Change the return type of qbt_poll from unsigned int
to __poll_t.

Change-Id: Ib43f6bb5ba77cb48d1e47e1ecd1d5b810f7c9159
Signed-off-by: Abir Ghosh <abirg@codeaurora.org>