scripts: python-devicetree: Expose dtlib properties

Using the python-devicetree library to display all nodes and properties
in the DT misses any properties either not part of the binding or covered
by the spec (e.g. #address-cells). This means tools loading devicetree
information from the pickled edt file have incomplete information. To
allow such tools to show a complete list of properties, expose the
dtlib dictionary of properties as a @Property in the edtlib Node class.

Signed-off-by: Graham Roff <grahamr@qti.qualcomm.com>

Author: grahamroff-dev