nvme-pci: remove nvme_pci_disable

nvme_pci_disable has a single caller, fold it into that.

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>