Andrew noticed that some handlers for *_SET commands leak a netdev
reference if required ethtool_ops callbacks do not exist. A simple
reproducer would be e.g.

  ip link add veth1 type veth peer name veth2
  ethtool -s veth1 wol g
  ip link del veth1

Make sure dev_put() is called when ethtool_ops check fails.

v2: add Fixes tags

Fixes: a53f3d41 ("ethtool: set link settings with LINKINFO_SET request")
Fixes: bfbcfe20 ("ethtool: set link modes related data with LINKMODES_SET request")
Fixes: e54d04e3 ("ethtool: set message mask with DEBUG_SET request")
Fixes: 8d425b19 ("ethtool: set wake-on-lan settings with WOL_SET request")
Reported-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Michal Kubecek <mkubecek@suse.cz>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>