before taking any steps further I want to decide which is better suited if I'm interested in robotics, control systems and autonomous cars.
I recall that, when I was at University (studied CS), my Mechatronic friends had several courses and topics regarding robotics, control systems, autonomous vehicles, etc. (in fact, those where the exact names of 3 courses they had), whereas I had other more software-oriented courses and topics.
If I where to chose between a CS and a Mechatronic student (assuming they are the same level of skill) for such job, I'd say that the Mechatronic student is more likely to be a better fit.
However, this is not as simple and straightforward as it seems. There could be a CS graduate that is better fit than a Mechatronic graduate, depending on the specific details and roles of the job.
If I decided to study computer science and specialize in AI and deep learning will I be a good candidate to work in robotics field? - even if I had to study more topics as self-study?
Like I said, A Mechatronic graduate could be a better fit.
However, AI is a really relevant topic for robotics, control systems and autonomous vehicles (in fact, AI encompasses those and many other subtopics), so having a strong knowledge of AI would be a good thing for someone looking for such kind of jobs. A "pure" Mechatronic engineer could be lacking a bit on AI and Deep Learning knowledge compared to a CS engineer.
Finally, as a suggestion/opinion, perhaps what you would like and what would be best for you would be to take the Mechatronic career, and complement it with elective courses on AI and related topics, so you can have the "best of both worlds".
These are suggestions. As it is your career and your life, I suggest you take this into consideration along with any other input you have, and then take an informed decision. Good luck with the change.