nvme: blank out authentication fabrics options if not configured

If the config option NVME_HOST_AUTH is not selected we should not
accept the corresponding fabrics options. This allows userspace
to detect if NVMe authentication has been enabled for the kernel.

Cc: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Fixes: f50fff73

 ("nvme: implement In-Band authentication")
Signed-off-by: Hannes Reinecke <hare@suse.de>
Tested-by: Shin'ichiro Kawasaki <shinichiro.kawasaki@wdc.com>
Reviewed-by: Daniel Wagner <dwagner@suse.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Keith Busch <kbusch@kernel.org>