I tested the r-pi2 image today with rpi3,and after manually updating the 
firmware files on sd card (except for kernel7.img), i got void to boot 
correctly on r-pi3. Otherwise i would be stuck on rainbow screen.

Official images are a bit outdated and only support r-pi2. Afaik there is 
already a raspberry pi firmware package in void repo that provides the 
necessary files. A simple arm image rebuild would resolve this problem.