It is difficult to give concrete advice without understanding your research in depth. From what I understand, you want to create a keyword cloud for the most common words used in the interviews. If the prominent words are an important finding that supports your research question, you will need to mention how you arrived at those words. So, logically speaking, you should include the keyword density analysis in the methods section.
However, it is impossible to say whether it is really necessary or relevant without going through your research in detail. I think it would be best if you can ask a senior colleague, your supervisor, or an expert in the field to be sure about this.