nvme-auth: fix an error code in nvme_auth_process_dhchap_challenge()

This function was transitioned from returning NVMe status codes to
returning traditional kernel error codes.  However, this particular
return now accidentally returns positive error codes like ENOMEM instead
of negative -ENOMEM.

Fixes: b0ef1b11 ("nvme-auth: don't use NVMe status codes")
Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

drivers/nvme/host/auth.c

@@ -254,7 +254,7 @@ static int nvme_auth_process_dhchap_challenge(struct nvme_ctrl *ctrl,
 				 chap->qid, ret, gid_name);
 			chap->status = NVME_AUTH_DHCHAP_FAILURE_DHGROUP_UNUSABLE;
 			chap->dh_tfm = NULL;
-			return -ret;
+			return ret;
 		}
 		dev_dbg(ctrl->device, "qid %d: selected DH group %s\n",
 			chap->qid, gid_name);