hw/block/nvme: fix namespaces array to 1-based

hw/block/nvme: fix namespaces array to 1-based

subsys->namespaces array used to be sized to NVME_SUBSYS_MAX_NAMESPACES.
But subsys->namespaces are being accessed with 1-based namespace id
which means the very first array entry will always be empty(NULL).

Signed-off-by: Minwoo Im <minwoo.im.dev@gmail.com>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Klaus Jensen <k.jensen@samsung.com>
Tested-by: Klaus Jensen <k.jensen@samsung.com>
Signed-off-by: Klaus Jensen <k.jensen@samsung.com>