nvme-auth: rename __nvme_auth_[reset|free] to nvme_auth[reset|free]_dhchap

nvme_auth_[reset|free] operate on the controller while
__nvme_auth_[reset|free] operate on a chap struct (which maps to a queue
context). Rename it for clarity.

Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>