This workflow runs only if there is a change to the kernel_module path.
Consequently, commits that only impact the kernel_module will be ignored
for the standard userspace driver build.
This commit also updates the CodeQL workflow to only run on a scheduled
basis and on pull requests, but not on every push, since this is a
fairly slow script.
Finally, this commit also removes the obsolete kernel module sources,
since they are no longer maintained, and it also provides a hook for
Github actions to pick up and execute the kernel workflow.
Ubuntu Trusty doesn't ship with a new enough pkg-config, which causes
the PKG_INSTALLDIR macro to fail on those systems. Since Trusty is EOL
anyway, simply disable the CI build on it.