hw/nvme: rework csi handling

hw/nvme: rework csi handling

The controller incorrectly allows a zoned namespace to be attached even
if CS.CSS is configured to only support the NVM command set for I/O
queues.

Rework handling of namespace command sets in general by attaching
supported namespaces when the controller is started instead of, like
now, statically when realized.

Reviewed-by: Jesper Wendel Devantier <foss@defmacro.it>
Signed-off-by: Klaus Jensen <k.jensen@samsung.com>