sgi-xp: link XPNET's net_device_ops to its net_device structure

A recent patch by Stephen Hemminger to convert XPNET to use net_device_ops and
internal net_device_stats failed to link the net_device_ops structure to the
net_device structure. See commit e8ac9c55
("xpnet: convert devices to new API").

Signed-off-by: Dean Nelson <dcn@sgi.com>
Signed-off-by: David S. Miller <davem@davemloft.net>