drm/sched: add drm_sched_fault

Add a helper to immediately start timeout handling in case of a hardware
fault.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Andrey Grodzovsky <andrey.grodzovsky@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>