fix(dracut-install): prevent possible infinite recursion with suppliers

fix(dracut-install): prevent possible infinite recursion with suppliers

During search for fw_devlink suppliers, it's possible to encounter a
situation where supplier A depends on supplier B, and supplier B has a
parent node that depends on supplier A. This leads to an infinite
recursion.

To fix this, make sure suppliers are only processed once.

Signed-off-by: Adrien Thierry <athierry@redhat.com>