net: ethtool: set a default driver name

The netdev (e.g. ifb, bareudp), which not support ethtool ops
(e.g. .get_drvinfo), we can use the rtnl kind as a default name.

ifb netdev may be created by others prefix, not ifbX.

Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Hao Chen <chenhao288@hisilicon.com>
Cc: Heiner Kallweit <hkallweit1@gmail.com>
Cc: "Gustavo A. R. Silva" <gustavoars@kernel.org>
Cc: Danielle Ratson <danieller@nvidia.com>
Cc: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Tonghao Zhang <xiangxia.m.yue@gmail.com>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Link: https://lore.kernel.org/r/20211125163049.84970-1-xiangxia.m.yue@gmail.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

net/ethtool/ioctl.c

@@ -734,6 +734,9 @@ ethtool_get_drvinfo(struct net_device *dev, struct ethtool_devlink_compat *rsp)
 			sizeof(rsp->info.bus_info));
 		strlcpy(rsp->info.driver, dev->dev.parent->driver->name,
 			sizeof(rsp->info.driver));
+	} else if (dev->rtnl_link_ops) {
+		strlcpy(rsp->info.driver, dev->rtnl_link_ops->kind,
+			sizeof(rsp->info.driver));
 	} else {
 		return -EOPNOTSUPP;
 	}