Since commit:

b99182c5 ("bio: add pcpu caching for non-polling bio_put")

we support bio caching for IRQ based IO as well, hence there's no need
to manually clear REQ_ALLOC_CACHE if we disable polling on a request.
Reviewed-by: NKeith Busch <kbusch@kernel.org>
Signed-off-by: NJens Axboe <axboe@kernel.dk>