Force arith on header in simple_switch
Force arith on header in simple_switch

Instead of forcing arith on each individual fields. This is less
error-prone in case a new field is added to one of the headers.
p4lang/behavioral-model,hanw/behavioral-model,hanw/behavioral-model,p4lang/behavioral-model,p4lang/behavioral-model,hanw/behavioral-model,p4lang/behavioral-model,hanw/behavioral-model,p4lang/behavioral-model,hanw/behavioral-model