Verify the surfaceType before activating the GL context

Verify the surfaceType before activating the GL context

Verify that the surfaceType() of the QPlatformContext is of type
OpenGLSurface before making the context active. Make it possible
to get the QSurface from a QPlatformSurface, make QPlatformWindow
use that to access the QWindow. Remove the setSurfaceType call from
the eglfs plugin as this hiding a problem.

Change-Id: I08906da052e066bb1f1f042030643c6389ab17d7
Reviewed-by: Samuel Rødal <samuel.rodal@nokia.com>
Reviewed-by: Girish Ramakrishnan <girish.1.ramakrishnan@nokia.com>