There is an updated pull request by Piraty against master on the void-packages repository

https://github.com/Piraty/void-packages rpi-kernel-fix-dkms
https://github.com/void-linux/void-packages/pull/14823

[WIP] rpi-kernel: enable build of kernel modules
Thanks to @marmeladema (#8480 ,  b5fa1bd9b6ec04c20bc1fe01540295200ef552d9) (and @Hoshpak for making me aware of this commit)

A patch file from https://github.com/void-linux/void-packages/pull/14823.patch is attached