tctx_task_work() may get run after io_uring cancellation and so there
will be no one to put cached in tctx task refs that may have been added
back by tw handlers using inline completion infra, Call
io_uring_drop_tctx_refs() at the end of the main tw handler to release
them.

Cc: stable@vger.kernel.org # 5.15+
Reported-by: NLukas Bulwahn <lukas.bulwahn@gmail.com>
Fixes: e98e49b2 ("io_uring: extend task put optimisations")
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/69f226b35fbdb996ab799a8bbc1c06bf634ccec1.1641688805.git.asml.silence@gmail.comSigned-off-by: NJens Axboe <axboe@kernel.dk>