LICENSE: Add the GPL-2.0 from the Linux kernel
Add the GPL v2.0 from https://raw.githubusercontent.com/torvalds/linux/master/LICENSES/preferred/GPL-2.0
The source code comes directly from the Linux kernel. So also take the original version of the license from there. It contains more than just the license Text but also the SPDX annotations. Keep on the safe side and use the original version.