utils/viewer: fix viewport coordinates
utils/viewer: fix viewport coordinates

Fixes a regression introduced by
180df017005a109e45fb38eb1feaf3ff68de8974 as the new QOpenGLWidget
overrides the viewport before each call to paintGL with the following
coordinates: 0, 0, self.width(), self.height()

gopro/gopro-lib-node.gl,gopro/gopro-lib-node.gl,gopro/gopro-lib-node.gl,gopro/gopro-lib-node.gl