The question is ambiguous. A penalty kick has a specific meaning in soccer. It is given when there is a direct free kick offense within the offender's own penalty area. It may or may not accompany misconduct; a caution or send off.
So, technically, there is no limit to the number of penalty kicks that could be awarded in a single soccer match. Although a referee would certainly start sanctioning for misconduct if there were such a pattern of fouls occurring.