livetree: add missing type markers in generated overlay properties

The YAML output fails for overlays and when symbol generation are enabled
due to missing markers in the generated properties.

Add type markers when generating properties under '__symbols__' and
'__fixups__' nodes as well as target-path properties. As a side effect of
append_to_property() changes, this also sets type markers in
'__local_fixups__' node properties.

Signed-off-by: Rob Herring <robh@kernel.org>
Message-Id: <20190517202804.9084-1-robh@kernel.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>