drm/i915/gvt: use hrtimer replace delayed_work in scheduler

Currently the scheduler is triggered by delayed_work, which doesn't
provide precision at microsecond level. Move to hrtimer instead for
more accurate control.

Signed-off-by: Ping Gao <ping.a.gao@intel.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>

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

@@ -144,6 +144,11 @@ static int gvt_service_thread(void *data)
 			intel_gvt_emulate_vblank(gvt);
 			mutex_unlock(&gvt->lock);
 		}
+
+		if (test_and_clear_bit(INTEL_GVT_REQUEST_SCHED,
+					(void *)&gvt->service_request)) {
+			intel_gvt_schedule(gvt);
+		}
 	}
 
 	return 0;