hw/nvme: Clean up local variable shadowing in nvme_ns_init()

Fix local variable shadowing in nvme_ns_init().

Reported-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Klaus Jensen <k.jensen@samsung.com>
Message-ID: <20230925-fix-local-shadowing-v1-1-3a1172132377@samsung.com>
Reviewed-by: Jesper Wendel Devantier <j.devantier@samsung.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>