io_uring: return back rsrc data free helper

Add io_rsrc_data_free() helper for destroying rsrc_data, easier for
search and the function will get more stuff to destroy shortly.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/562d1d53b5ff184f15b8949a63d76ef19c4ba9ec.1619356238.git.asml.silence@gmail.com


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