ixgbe: Remove ATR computation for UDP traffic

ATR support for UDP on 82599 needs to be redesigned, since the
current model doesn't make much sense.  The fallout from having
it in though is it causes all UDP traffic to still compute the
ATR hashes on transmit, which are useless.  This removal will
return upwards of 10% of relative computational overhead in
forwarding tests.

Signed-off-by: Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>