Add policy for 'blank_screen'.

This util allows init to turn off the screen
without any binder dependencies.

Bug: 70846424
Test: manual + init use
Change-Id: I4f41a966d6398e959ea6baf36c2cfe6fcebc00de
diff --git a/private/blank_screen.te b/private/blank_screen.te
new file mode 100644
index 0000000..43d273b
--- /dev/null
+++ b/private/blank_screen.te
@@ -0,0 +1,6 @@
+type blank_screen, domain, coredomain;
+type blank_screen_exec, exec_type, file_type;
+
+init_daemon_domain(blank_screen)
+
+hal_client_domain(blank_screen, hal_light)