Merge branch 'opt/register-ring-fd' of https://github.com/calebsander/fio

* 'opt/register-ring-fd' of https://github.com/calebsander/fio:
  io_uring: try to register ring fd
  io_uring: consolidate fio_ioring{,_cmd}_post_init()
  io_uring: consolidate fio_ioring{,_cmd}_queue_init()