The signature/hash information are displayed for images but nor for
configurations.
Add subnodes printing in fit_conf_print() like it's done in fit_image_print()
Signed-off-by: Clément Péron <peron.clem@gmail.com>
[trini: Add guards around fit_conf_print to avoid warnings]
Signed-off-by: Tom Rini <trini@konsulko.com>