drm/radeon: update lockup tracking when scheduling in empty ring

There might be issue with lockup detection when scheduling on an
empty ring that have been sitting idle for a while. Thus update
the lockup tracking data when scheduling new work in an empty ring.

Signed-off-by: Jerome Glisse <jglisse@redhat.com>
Tested-by: Andy Lutomirski <luto@amacapital.net>
Cc: stable@vger.kernel.org
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>