ice: switch: use convenience macros to declare dummy pkt templates

Declarations of dummy/template packet headers and offsets can be
minified to improve readability and simplify adding new templates.
Move all the repetitive constructions into two macros and let them
do the name and type expansions.
Linewrap removal is yet another positive side effect.

Signed-off-by: Alexander Lobakin <alexandr.lobakin@intel.com>
Reviewed-by: Michal Swiatkowski <michal.swiatkowski@linux.intel.com>
Tested-by: Marcin Szycik <marcin.szycik@linux.intel.com>
Tested-by: Sandeep Penigalapati <sandeep.penigalapati@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>