ixgbe: Fix DCB traffic class mapping for 82599

The traffic classes in hardware are not symmetrical for Rx and Tx.  Rx
is every 16 descriptor queues, Tx is not.  It runs 32-32-16-16-8-8-8 when
running with 8 traffic classes, and runs 64-32-16 when running with 4
traffic classes.  This patch fixes the mapping.

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