JEE Advance Does not have fixed chapter wise weightage. Every year's pattern also changes like in 2015 they introduced -2 marking, in 2016 partial marking is introduced. Sometimes they ask questions more on some topic and less on other but next year opposite. So you can not get any pattern in the number of questions asked from each chapter.

You can do one thing just check the Previous year's distribution of questions from each chapter to get an idea of which chapter is more important over the others. But there is certainly very fewer chances that you come to a conclusion regarding Weightage. You should prepare for each chapter from basics and you must be conceptually sound to solve JEE Advance questions.