ixgbe: fix select_queue management

Convert ixgbe to use net_device_ops properly.
Rather than changing the select_queue function pointer
just check the flag.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Acked-by: Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>