ixgbe: ethtool DCB registers dump for 82599 and x540

Added support for DCB registers dump using ethtool -d option both for
82599 and x540 ethernet controllers

Signed-off-by: Leonardo Potenza <leonardo.potenza@intel.com>
Signed-off-by: Maryam Tahhan <maryam.tahhan@intel.com>
Acked-by: John Fastabend <john.r.fastabend@intel.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Tested-by: Jack Morgan <jack.morgan@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>