hal_power_stats: use hal_attribute_service

This macro creates the necessary neverallow to assert the
hal_power_stats_{client,server} attribute has exclusive ownership of
the service.

Bug: 176180039
Test: build/TH
Change-Id: I710eadc4c4f4642937aa16a25fe559e1cd3c9224
diff --git a/public/hal_power_stats.te b/public/hal_power_stats.te
index b989e2e..f458db6 100644
--- a/public/hal_power_stats.te
+++ b/public/hal_power_stats.te
@@ -3,8 +3,6 @@
 binder_call(hal_power_stats_server, hal_power_stats_client)
 
 hal_attribute_hwservice(hal_power_stats, hal_power_stats_hwservice)
+hal_attribute_service(hal_power_stats, hal_power_stats_service)
 
-add_service(hal_power_stats_server, hal_power_stats_service)
 binder_call(hal_power_stats_server, servicemanager)
-
-allow hal_power_stats_client hal_power_stats_service:service_manager find;