drm/i915/gvt: clean workload queue if error happened

If a workload caused a HW GPU hang or it is in the middle of
vGPU reset, the workload queue should be cleaned up to emulate
the hang state of the GPU.

v2:
- use ENGINE_MASK(ring_id) instead of (1 << ring_id). (Zhenyu)

Signed-off-by: Chuanxiao Dong <chuanxiao.dong@intel.com>
Cc: Zhenyu Wang <zhenyuw@linux.intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>