fs: aio: initialize .ki_write_stream of read-write request

AIO needs to initialize .ki_write_stream explicitly for read/write request,
otherwise random .ki_write_stream is used, and cause -EINVAL returned for
aio write randomly.

Cc: Christoph Hellwig <hch@lst.de>
Cc: Keith Busch <kbusch@kernel.org>
Cc: Kanchan Joshi <joshi.k@samsung.com>
Fixes: c27683da ("block: expose write streams for block device nodes")
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20250507133328.3040255-1-ming.lei@redhat.com


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