ixgbe: Re-adjust ring layouts to have better cacheline efficiency

This patch rearranges the ixgbe_ring struct to make better use of
cacheline efficiency.

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