Check for ethtool_ops structures that are only stored in the ethtool_ops
field of a net_device structure or passed as the second argument to
netdev_set_default_ethtool_ops. These contexts are declared const, so
ethtool_ops structures that have these properties can be declared as const
also.
The semantic patch that makes this change is as follows:
(http://coccinelle.lip6.fr/)