OpenGL issues on Mali T628 (ODroid XU3)

The following issues have been encountered so far when testing on an ODroid-XU3, both on fbdev and X11:

• QOpenGLWidget does not work at all. Somehow related to the FBO. No GL errors are given and the FBO seems to be complete. -> https://codereview.qt-project.org/#/c/108997

• Even after the above fix the qopenglwidget example behaves odd: disable the timer and start adding new QOpenGLWidgets to the window. At some point they will just stop animating.

• Quick apps using multisampled FBOs are broken (textureinsgnode example). Incomplete attachments.

• The basic QQuickWidget example (quickwidget) is broken and features surreal mirrored textures after some clicking. The advanced one (qquickviewcomparison) works, though. -> https://codereview.qt-project.org/#/c/109005/

• The textures example from qtbase has no textures on the sides of the cubes. QOpenGLTexture issue? -> disabled immutable storage for Mali in https://codereview.qt-project.org/#/c/109011/

• No vsync, or at least it is surely not 60 Hz. (X11) Not sure on fbdev, then again it does not really matter there because the driver is way too slow anyhow. -> to be fixed in the driver