ice: mark PTYPE 2 as reserved

The entry for PTYPE 2 in the ice_ptype_lkup table incorrectly states
that this is an L2 packet with no payload. According to the datasheet,
this PTYPE is actually unused and reserved.

Fix the lookup entry to indicate this is an unused entry that is
reserved.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Tony Brelinski <tonyx.brelinski@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>