Router have 3 power lines: +3.3v, +1.8v and +5v. +5v is always on and used to switch other lines on through power button and for something else. Power switching made of transistor key, when you push power button, transistor key opens and enable +3.3v and +1.8v power lines.
All we need is just short this key like on picture. You need a small piece of wire. Solder one end to plus side of power socket and second end to plus side of one of capacitors which you can see on the left of arrow. You should get something like on picture on the right. That's all.
Toolchains setup for software mods next, stay tuned.