io_uring/rw: enable bio caches for IRQ rw

Now we can use IOCB_ALLOC_CACHE not only for iopoll'ed reads/write but
also for normal IRQ driven I/O.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/fb8bd092ed5a4a3b037e84e4777074d07aa5639a.1667384020.git.asml.silence@gmail.com


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