io_uring: ensure deferred timeouts copy necessary data

If we defer a timeout, we should ensure that we copy the timespec
when we have consumed the sqe. This is similar to commit f67676d1
for read/write requests. We already did this correctly for timeouts
deferred as links, but do it generally and use the infrastructure added
by commit 1a6b74fc

 instead of having the timeout deferral use its
own.

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