io_uring/zcrx: init id for xa_find

xa_find() interprets id as the lower bound and thus expects it initialised.

Reported-by:  <syzbot+c3ff04150c30d3df0f57@syzkaller.appspotmail.com>
Fixes: 76f1cc98 ("io_uring/zcrx: add support for multiple ifqs")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/faea44ef63131e6968f635e1b6b7ca6056f1f533.1748359655.git.asml.silence@gmail.com


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