egl/dri2: glFlush is not optional, treat it as such

The documentation is clear - one must glFlush the old context on
eglMakeCurrent. Thus keeping it optional is not something we should be
doing. Furthermore if we cannot get the entry point we're likely having
a broken setup/stack.

Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Eric Engestrom <eric.engestrom@imgtec.com>
1 file changed