ldmvsw: disable tso and gso for bridge operations

The ldmvsw driver is specifically for supporting the ldom virtual
networking by running in the primary ldom and using the LDC to connect
the remaining ldoms to the outside world via a bridge.  With TSO and GSO
supported while connected the bridge, things tend to misbehave as seen
in our case by delayed packets, enough to begin triggering retransmits
and affecting overall throughput.  By turning off advertised support for
TSO and GSO we restore stable traffic flow through the bridge.

Orabug: 23293104

Signed-off-by: Shannon Nelson <shannon.nelson@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>