python3-sdbus++: switch to native setuptools3

The sdbusplus repository now has a real setup.py file that doesn't
require autotools generation.  Switch to a normal setuptools3
recipe.

(From meta-phosphor rev: 1914bbb37e7307f9f96b2c752f8df8f7699463cf)

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I31bac1fcc061cc0195fb7d3accf922ec57852ba1
Signed-off-by: Andrew Geissler <geissonator@yahoo.com>