mako: Support interfaces without property

If a settings interface contains no property, the code get compiles
failure that the cereal does not know how to de-serialize the object.

It turns out that if an interface has no property, it does not need to
serialize/de-serialize the properties at all.

Add a check in mako to skip the above for interfaces without properties,
and then the code compiles fine.

Tested: Verify we could add an interface without property to a DBus
        object, e.g. xyz.openbmc_project.Inventory.Item.Bmc

Signed-off-by: Lei YU <yulei.sh@bytedance.com>
Change-Id: I68a9e689c2e2a9da65c8b090ac925baebd27733a
1 file changed