Add fwk_display_hwservice.

This hidl service provides information about vsync and hotplug
to vendor services which is required by at least some camera
hal implementations.

Test: VtsFwkDisplayServiceV1_0TargetTest
Test: no denials
Bug: 38311538
Change-Id: I64f0321e2832facf987057f0d48940e269d8e2d9
diff --git a/private/hwservice_contexts b/private/hwservice_contexts
index ecac57e..35c95ce 100644
--- a/private/hwservice_contexts
+++ b/private/hwservice_contexts
@@ -1,3 +1,4 @@
+android.frameworks.displayservice::IDisplayService              u:object_r:fwk_display_hwservice:s0
 android.frameworks.schedulerservice::ISchedulingPolicyService   u:object_r:fwk_scheduler_hwservice:s0
 android.frameworks.sensorservice::ISensorManager                u:object_r:fwk_sensor_hwservice:s0
 android.hardware.audio.effect::IEffectsFactory                  u:object_r:hal_audio_hwservice:s0