python-devicetree: bump version to 0.0.2

Inconsistency between python-devicetree version numbers
may be confusing:
- the last version at PyPI is 0.0.2
- zephyr-rtos/python-devicetree/setup.py sets the version
  to 0.0.2 (this is probably the setup file used when uploading
  to PyPI)
- zephyr-rtos/zephyr/scripts/dts/python-devicetree/setup.py sets
  the version to 0.0.1

This may suggest that the mirror repository, and PyPI, are more
up-to-date than zephyr-rtos/zephyr/scripts/dts/python-devicetree.

Repositories being otherwise mostly identical (1), also bumping
the python-devicetree's version here seems a sane option.

(1) Ignoring the doc directory (only at zephyr-rtos/python-devicetree).

Signed-off-by: Chris Duf <chris@openmarl.org>