We've got some sample config files in docs/config/ but no means
of regression checking them. Thus let's test them in our readconfig
qtest, starting with ich9-ehci-uhci.cfg. Note: To enable the test
to read the config files from the build folder, we have to install
a symlink for docs/config in the build directory.

Message-Id: <20230228211533.201837-3-thuth@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>