ice: Report correct DCB mode

Add code to detect if DCB is in IEEE or CEE mode. Without this the code
will always report as IEEE mode which is incorrect and confuses the
user.

Signed-off-by: Avinash Dayanand <avinash.dayanand@intel.com>
Signed-off-by: Scott Register <scottx.register@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>