Don't reset if the engine isn't busy.  This matches the behavior of
previous asics.  Reseting a non-hung block can lead to a hang.

Fixes:
https://bugs.freedesktop.org/show_bug.cgi?id=33272Signed-off-by: NAlex Deucher <alexdeucher@gmail.com>
Signed-off-by: NDave Airlie <airlied@gmail.com>