Yes it is very beneficiary if ece student goes for M.Tech in aerospace engineering if there is a dying thirst to pursue it. You could cope on due course of time. But there i s another option available named avionics open to electronics engineers. You could opt for it. For that one EC paper in gate would be sufficient.

some avionics courses links , which link aero  and ECE: Aviation Electronics Technology - Avionics systems program , The Aircraft Electronics Association , Online Avionics Courses and Schools

Write your GATE/GRE exam well and you can pursue Aerospace in your Masters. All the best for your future. Hope this information helps you chase your dream.

I am aiming for the same.

Cheers!!

Good luck:)