drm/i915/gvt: cancel scheduler timer when no vGPU exists

Stop gvt scheduler timer if no vGPU exists, otherwise it keeps
gvt service thread busy to handle request schedule event but no
actual schedule activity required.
Reviewed-by: NZhi Wang <zhi.a.wang@intel.com>
Signed-off-by: NZhenyu Wang <zhenyuw@linux.intel.com>
Signed-off-by: NRodrigo Vivi <rodrigo.vivi@intel.com>

drivers/gpu/drm/i915/gvt/sched_policy.c

@@ -308,8 +308,15 @@ static int tbs_sched_init_vgpu(struct intel_vgpu *vgpu)
 
 static void tbs_sched_clean_vgpu(struct intel_vgpu *vgpu)
 {
+	struct intel_gvt *gvt = vgpu->gvt;
+	struct gvt_sched_data *sched_data = gvt->scheduler.sched_data;
+
 	kfree(vgpu->sched_data);
 	vgpu->sched_data = NULL;
+
+	/* this vgpu id has been removed */
+	if (idr_is_empty(&gvt->vgpu_idr))
+		hrtimer_cancel(&sched_data->timer);
 }
 
 static void tbs_sched_start_schedule(struct intel_vgpu *vgpu)