See if you clear the GATE Electrical paper then obviously you are eligible for the PSU but you need to have satisfy the qualification eligibility as asked by the PSU you are applying in. At this moment, if you search for the basic qualifications of most of the psu then there are no such eligibility conditions through which you can apply. So its better for you to pursue your MTech in a more broader field and then you can apply for jobs or postitions. Although Mechatronics is a vast subject and there are need of such engineers in different sectors such as Air Force,Aircraft Engineering, Oceanography, Oil and Gas etc. So there are chances for you to get chances in Mechanical Engineering related field of expertise. So its better for you to qualify GATE MECHANICAL than Electrical. That way you may get scope in PSU who have eligibility criteria of Mechanical Engineering.

To know more about GATE visit the link below:

https://engineering.careers360.com/articles/gate

I hope this answer helps. All the very best for your future endeavors!