iavf: clean up packet type lookup table

Remove the unused ptype struct value, which makes table init easier for
the zero entries, and use ranged initializer to remove a bunch of code
(works with gcc and clang). There is no significant functional change.

Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>