io_uring: optimise io_req_set_rsrc_node()

io_req_set_rsrc_node() reloads loads req->ctx, however it's already in
registers in all use cases, so better to pass it as a parameter.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/67a25557b8a51e90bfd578447a6f1671911b05ae.1633817310.git.asml.silence@gmail.com


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