devlink: fix net namespace reference leak in reload

devlink_nl_reload_doit() calls devlink_netns_get(), which returns a net
with a held reference. When the requested namespace differs from the
current one and the reload action is not DRIVER_REINIT, the function
returns -EOPNOTSUPP without releasing the reference. Add the missing
put_net() on this error path.

Fixes: 2edd925704 ("devlink: don't allow to change net namespace for FW_ACTIVATE reload action")
Signed-off-by: Or Har-Toov <ohartoov@nvidia.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Reviewed-by: Antoine Tenart <atenart@kernel.org>
Link: https://patch.msgid.link/20260729080600.2427721-1-tariqt@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/devlink/dev.c

@@ -578,6 +578,7 @@ int devlink_nl_reload_doit(struct sk_buff *skb, struct genl_info *info)
 		    action != DEVLINK_RELOAD_ACTION_DRIVER_REINIT) {
 			NL_SET_ERR_MSG_MOD(info->extack,
 					   "Changing namespace is only supported for reinit action");
+			put_net(dest_net);
 			return -EOPNOTSUPP;
 		}
 	}