io_uring: implement compat handling for IORING_REGISTER_IOWQ_AFF

commit 0f5e4b83 upstream.

Similarly to the way it is done im mbind syscall.

Cc: stable@vger.kernel.org # 5.14
Fixes: fe76421d ("io_uring: allow user configurable IO thread CPU affinity")
Signed-off-by: Eugene Syromiatnikov <esyr@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>