Fixes gcc '-Wunused-but-set-variable' warning:

drivers/net/ethernet/mellanox/mlxsw/spectrum.c: In function 'mlxsw_sp_port_get_link_ksettings':
drivers/net/ethernet/mellanox/mlxsw/spectrum.c:3062:5: warning:
 variable 'autoneg_status' set but not used [-Wunused-but-set-variable]

It's not used since commit 475b33cb ("mlxsw: spectrum: Remove unsupported
eth_proto_lp_advertise field in PTYS")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Reviewed-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>