io_uring: kbuf: inline io_kbuf_recycle_ring()

Make io_kbuf_recycle_ring() inline since it is the fast path of
provided buffer.

Signed-off-by: Hao Xu <howeyxu@tencent.com>
Link: https://lore.kernel.org/r/20220623130126.179232-1-hao.xu@linux.dev


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