This also fixes:
- confusion around vlan_features in rtl8169_vlan_mode(),
- problem with broken TSO for too big MTU (the limit is set
at 0xFFF --- max MSS field value).
SG+IP_CSUM+TSO is left disabled by default, based on suggestion by
David Dillow.
Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl> Signed-off-by: David S. Miller <davem@davemloft.net>