net: phy: Make phy_ethtool_ksettings_get return void

Make return value void since function never return meaningfull value

Signed-off-by: Yuval Shaia <yuval.shaia@oracle.com>
Acked-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: David S. Miller <davem@davemloft.net>