net: asix: add missing flag to struct driver_info

The struct driver_info ax88178_info is assigned the function
asix_rx_fixup_common as it's rx_fixup callback. This means that
FLAG_MULTI_PACKET must be set as this function is cloning the
data and calling usbnet_skb_return. Not setting this flag leads
to usbnet_skb_return beeing called a second time from within
the rx_process function in the usbnet module.

Signed-off-by: Emil Goode <emilgoode@gmail.com>
Reported-by: Bjørn Mork <bjorn@mork.no>
Signed-off-by: David S. Miller <davem@davemloft.net>