drm/i915/gvt: Support event based scheduling

This patch decouple the time slice calculation and scheduler, let
other event be able to trigger scheduling without impact the
calculation for QoS.

v2: add only one new enum definition.
v3: fix typo.

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

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

@@ -147,7 +147,9 @@ static int gvt_service_thread(void *data)
 			mutex_unlock(&gvt->lock);
 		}
 
-		if (test_and_clear_bit(INTEL_GVT_REQUEST_SCHED,
+		if (test_bit(INTEL_GVT_REQUEST_SCHED,
+				(void *)&gvt->service_request) ||
+			test_bit(INTEL_GVT_REQUEST_EVENT_SCHED,
 					(void *)&gvt->service_request)) {
 			intel_gvt_schedule(gvt);
 		}