ixgbe: DCB during ifup use correct CEE or IEEE mode

DCB settings are cleared in the hardware across link events
during ifup ixgbe reprograms the hardware for DCB if it is
enabled. Now that we have two modes CEE or IEEE we need to
use the correct set of configuration data.

This patch checks the dcbx_cap bits and then enables the
device in the correct mode.

Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
Tested-by: Ross Brattain <ross.b.brattain@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>