Hi Govind, if AMP pages are not primary URLs of your website then sitemap xml is not required. And if AMP urls are alternate pages of primary URL the it will discovered by google crawlers automatically by using <amphtml> tag. So take actions accordingly.
For example: your website primary URL is https://digirank.in
and alternate URL with AMP template is https://digirank.in/amp.
So in this case separate sitemap or sitemap having amp URLs are not required.