package/python-simplegeneric: Switch setup type to 'setuptools'

package/python-simplegeneric: Switch setup type to 'setuptools'

Specifying setup type to be 'distutils' results in this package being
installed as .egg, a zipped file, which inadvertantly makes
'simplegeneric' to be dependent on BR2_PACKAGE_PYTHON*_ZLIB. In order
to avoid that specify setup type to be 'setuptools' which makes use of
--single-version-externally-managed and therefore installs the package
as .pyc and a .egg-info folder.

Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Reviewed-by: Yegor Yefremov <yegorslists@googlemail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>