ice: add and use new ice_for_each_traffic_class() macro

There are numerous for() loops iterating over each of the max traffic
classes.  Use a simple iterator macro instead to make the code cleaner.

Signed-off-by: Bruce Allan <bruce.w.allan@intel.com>
Signed-off-by: Anirudh Venkataramanan <anirudh.venkataramanan@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>