This just adds skeleton code/yaml files to enable gating for
linux-firmware. There is no actual testing done, we just return success
result (with true command). linux-firmware is special, in which we don't
ship any executable, and we don't have any useful test cases. We
expect tests are already done by companies which ship/submit firmware to
the linux-firmware repository upstream.
Resolves: rhbz#1680622
Signed-off-by: Herton R. Krzesinski <herton@redhat.com>