net: phy: fix uninitalized ethtool_wolinfo in phy_suspend

Callers of phy_ethtool_get_wol are supposed to provide a properly
cleared struct ethtool_wolinfo. Therefore, fix phy_suspend to clear
it before passing it to phy_ethtool_get_wol.

Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>
Reviewed-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>