nvmet-auth: replace pr_debug() with pr_err() to report an error.

In nvmet_auth_host_hash(), if a mismatch is detected in the hash length
the kernel should print an error.

Signed-off-by: Maurizio Lombardi <mlombard@redhat.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>