ethtool: allow ETHTOOL_GSSET_INFO for users

Allow ETHTOOL_GSSET_INFO ethtool ioctl() for unprivileged users.
ETHTOOL_GSTRINGS is already allowed, but is unusable without this one.

Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Acked-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>