net/{mii, smsc}: Make mii_ethtool_get_link_ksettings and smc_netdev_get_ecmd return void

Make return value void since functions never returns meaningfull value.

Signed-off-by: Yuval Shaia <yuval.shaia@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>