Fix build on RHEL 9.7 and 10.1 kernels - #543

• EL 9.7 and 10.1 kernels have many backports from later releases; up to 6.15.
  • Add the necessary definitions to fix building.
• Starting from EL 10.1, the VERSION_ID variable in /etc/os-release prints out the minor version as well, so the generation of the -DEL<version> definition fails.
  • Cut to the first dot, so it works for both EL10 and EL8/EL9.
  • Note that CentOS Stream still reports only 10.

Tested with the following kernels:

EL 8.10 - 4.18.0-553.85.1.el8_10.x86_64
EL 9.7 - 5.14.0-611.5.1.el9_7.x86_64
EL 10.1 - 6.12.0-124.8.1.el10_1.x86_64