nvme: forward port sysfs delete fix

We had a late fix that modified nvme_sysfs_delete() after the staging
branch for the next merge window relocated the function to a new file.
Port commit 2eb94dd5 ("nvme: do not let the user delete a ctrl
before a complete") to the latest to avoid a potentially confusing merge
conflict.

Cc: Maurizio Lombardi <mlombard@redhat.com>
Cc: Max Gurtovoy <mgurtovoy@nvidia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Keith Busch <kbusch@kernel.org>