python-pyqt5: fix the build with Qt 5.6.2

python-pyqt5: fix the build with Qt 5.6.2

This commit adds a patch to the python-pyqt5 package that fixes the
build with Qt 5.6.2.

It has been verified to fix:

  http://autobuild.buildroot.net/results/8ca61ec09cf0e6577d72fe5d809867aa284c8f1e/

And it should also fix:

  http://autobuild.buildroot.net/results/4e0c5776264a7382c842f04e333fe4ded7d14f8a/
  http://autobuild.buildroot.net/results/0306710e0f39591dba74f24aff40f7f094bcfa6e/

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>