drm/i915/gvt: free workload in vgpu release

Some workloads may be prepared in vgpu's queue but not be scheduled
to run yet. If vgpu is released at this time, they will not be freed
in workload complete callback and so need to be freed in vgpu release
operation.

Add new vgpu_release operation in gvt_ops to stop vgpu and release
runtime resources. gvt_ops vgpu_deactivate operation will only stop
vgpu.

v2: add new gvt ops to clean vgpu running status (Xiong Zhang)

Signed-off-by: Hang Yuan <hang.yuan@linux.intel.com>
Reviewed-by: Xiong Zhang <xiong.y.zhang@intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>