Add ppc64le in setup.py to avoid build error

===
swig -python -D__ppc64le__ -I/usr/include/python3.6m -I/usr/include/ \
-includeall -modern -builtin -outdir \
/home/abuild/rpmbuild/BUILD/M2Crypto-0.27.0/M2Crypto \
-o SWIG/_m2crypto_wrap.c SWIG/_m2crypto.i
/usr/include//gnu/stubs.h:8: Error: Unable to find 'gnu/stubs-32.h'
error: command 'swig' failed with exit status 1
error: Bad exit status from /var/tmp/rpm-tmp.ugv4sN (%build)
===

Signed-off-by: Michel Normand <normand@linux.vnet.ibm.com>