drm/msm: add basic hangcheck/recovery mechanism

A basic, no-frills recovery mechanism in case the gpu gets wedged.  We
could try to be a bit more fancy and restart the next submit after the
one that got wedged, but for now keep it simple.  This is enough to
recover things if, for example, the gpu hangs mid way through a piglit
run.

Signed-off-by: Rob Clark <robdclark@gmail.com>