nvme-auth: fix smatch warning complaints

When initializing auth context, there may be no secrets passed
by the user. Make return code explicit when returning successfully.

smatch warnings:
drivers/nvme/host/auth.c:950 nvme_auth_init_ctrl() warn: missing error code? 'ret'
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>

drivers/nvme/host/auth.c

@@ -953,7 +953,7 @@ int nvme_auth_init_ctrl(struct nvme_ctrl *ctrl)
 		goto err_free_dhchap_secret;
 
 	if (!ctrl->opts->dhchap_secret && !ctrl->opts->dhchap_ctrl_secret)
-		return ret;
+		return 0;
 
 	ctrl->dhchap_ctxs = kvcalloc(ctrl_max_dhchaps(ctrl),
 				sizeof(*chap), GFP_KERNEL);