drm/msm/gpu: Add some WARN_ON()s

We don't expect either of these conditions to ever be true, so let's get
shouty if they are.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Link: https://lore.kernel.org/r/20211124214151.1427022-6-robdclark@gmail.com


Signed-off-by: Rob Clark <robdclark@chromium.org>