Hello Vikas,
First of all I suggest you to choose the stream or field, which you like, in which you are interested. Choosing a right career option is the most important decision in a student life, so if you are interested in science, it is well and good.
You can fight for UPSC exams irrespective of any stream you choose. The syllabus of UPSC exams consist a significant portion of general science, so it will obviously helpful to you in your UPSC exam.
One more thing i would say that most of the candidates who clear UPSC exams are from science stream.
I hope you got your answer. All the best.