nvme_ns_realize passes errp to nvme_register_namespaces, but then try to
prepend errp with local_err.

Just remove the local_err and use errp directly.

Fixes: 15d024d4 ("hw/block/nvme: split setup and register for namespace")
Cc: Minwoo Im <minwoo.im.dev@gmail.com>
Reviewed-by: Minwoo Im <minwoo.im.dev@gmail.com>
Signed-off-by: Klaus Jensen <k.jensen@samsung.com>