nvme-apple: fix controller shutdown in apple_nvme_disable

nvme_shutdown_ctrl already shuts the controller down, there is no
need to also call nvme_disable_ctrl for the shutdown case.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Keith Busch <kbusch@kernel.org>
Reviewed-by: Eric Curtin <ecurtin@redhat.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Hector Martin <marcan@marcan.st>