devlink: add value check to devlink_info_version_put()

Prevent from proceeding if there's nothing to print.

Suggested-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Reviewed-by: Kalesh AP <kalesh-anakkur.purayil@broadcom.com>
Tested-by: Bharath R <bharath.r@intel.com>
Signed-off-by: Jedrzej Jagielski <jedrzej.jagielski@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

net/devlink/dev.c

@@ -775,7 +775,7 @@ static int devlink_info_version_put(struct devlink_info_req *req, int attr,
 		req->version_cb(version_name, version_type,
 				req->version_cb_priv);
 
-	if (!req->msg)
+	if (!req->msg || !*version_value)
 		return 0;
 
 	nest = nla_nest_start_noflag(req->msg, attr);