Draft: [arm64] Provide an installer package for usbgadget usage

The configfs module must be included explicitly in the kernel image udeb because currently it's included automatically in the scsi udeb as some modules in there depend on it and libcomposite also depends on it.

For now it's only enabled on arm64, but could be used on other archs, too. Tested on an machine with a Rockchip SoC (rk3568-qnap-ts433).