According to the txd_version, split rtl8169_tso_csum() into
rtl8169_tso_csum_v1() and rtl8169_tso_csum_v2().
Signed-off-by: NHayes Wang <hayeswang@realtek.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>