package/python-pyqt5: QtSvg needs QtWidgets

package/python-pyqt5: QtSvg needs QtWidgets

Building QtSvg without QtWidgets results in the following build failure:

/tmp/instance-0/output-1/host/bin/powerpc64le-linux-g++ -c -pipe -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -Os --sysroot=/tmp/instance-0/output-1/host/powerpc64le-buildroot-linux-gnu/sysroot -fno-exceptions -Wall -Wextra -D_REENTRANT -fPIC -DSIP_PROTECTED_IS_PUBLIC -Dprotected=public -DQT_NO_DEBUG -DQT_PLUGIN -DQT_SVG_LIB -DQT_GUI_LIB -DQT_CORE_LIB -I. -I. -I../../../host/powerpc64le-buildroot-linux-gnu/sysroot/usr/include/python3.8 -I../../../host/powerpc64le-buildroot-linux-gnu/sysroot/usr/include/qt5 -I../../../host/powerpc64le-buildroot-linux-gnu/sysroot/usr/include/qt5/QtSvg -I../../../host/powerpc64le-buildroot-linux-gnu/sysroot/usr/include/qt5/QtGui -I../../../host/powerpc64le-buildroot-linux-gnu/sysroot/usr/include/qt5/QtCore -I. -I../../../host/mkspecs/devices/linux-buildroot-g++ -o sipQtSvgcmodule.o sipQtSvgcmodule.cpp
sip/QtWidgets/qwidget.sip:28:10: fatal error: qwidget.h: No such file or directory
compilation terminated.
sip/QtWidgets/qgraphicsitem.sip:26:10: fatal error: qgraphicsitem.h: No such file or directory
compilation terminated.

Fixes:
 - http://autobuild.buildroot.org/results/26f55a1fa9f6520ce449b98b40d98f984cec07b3

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>