net: usb: ax88179_178a: add TSO feature

On low-effciency embedded platforms, transmission performance is poor
due to on Bulk-out with single packet.
Adding TSO feature improves the transmission performance and reduces
the number of interrupt caused by Bulk-out complete.

Reference to module, net: usb: aqc111.

Signed-off-by: Jacky Chou <jackychou@asix.com.tw>
Signed-off-by: David S. Miller <davem@davemloft.net>