nvme: consolodate io settings

The stream parameters indicating optimal io settings were just getting
overwritten later. Rearrange the settings so the streams parameters can
be preserved if provided.

Signed-off-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>