Actually correspondence B.Tech is not recognised as per the new rules and guidelines. This is as per the Supreme Court judgement passed in 2017. As far as I see some professional institutes may be allowed but these are also not recognized as per the court's ruling. check the eligibility here - http://gate.iitm.ac.in/Eligible

So I think that you may not be eligible but please write to IIT Madras for better clarification or call them up.