python-netifaces: enable on Python 3

Version 0.10.4 is compatible with python 3.

[Thomas: change the patch to simply remove the dependency on
BR2_PACKAGE_PYTHON, so that the package can be seen when either python
or python3 are used.]

Signed-off-by: Simon Marchi <simon.marchi@polymtl.ca>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>