ixgbe: SR-IOV: dynamic IEEE DCBx default priority changes

IEEE DCBx has a mechanism to change the default user priority. In
the normal case the OS can handle this via cgroups, iptables, socket,
options etc.

With SR-IOV and direct assigned VF devices the default priority
needs to be set by the PF device so the inserted VLAN tag is
correct.

Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Tested-by: Marcus Dennis <marcusx.e.dennis@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>