io_uring/rsrc: remove rsrc_data refs

Instead of waiting for rsrc_data->refs to be downed to zero, check
whether there are rsrc nodes queued for completion, that's easier then
maintaining references.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/8e33fd143d83e11af3e386aea28eb6d6c6a1be10.1681395792.git.asml.silence@gmail.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>