i40e: add DCB and DCBNL support

This patch adds capability to configure DCB on i40e network
interfaces using Intel XL710 adapter firmware APIs.

By default all VSIs are only enabled for the default traffic
class enabled by firmware for any given PF. The driver would
query the firmware for the traffic classes that are enabled for
the port and reconfigure the LAN VSI to match to the port traffic
class settings. All other VSIs are only enabled for the default
traffic class settings for now.

The driver registers and listens to firmware events that may
require change in the DCB settings. It may reconfigure the VSI
settings based on these events.

This patch exposes IEEE DCBNL interfaces for the i40e driver to
allow any application to query the DCB settings on the adapter.

Signed-off-by: Neerav Parikh <Neerav.Parikh@intel.com>
Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Tested-By: Jack <Morgan&lt;jack.morgan@intel.com>
Signed-off-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>