system_server: add hal_lights permission

system_server needs the permissions to open the lights hal in the same
process.

Bug: 34634317
Test: can change brightness on marlin (tested on internal master)
Change-Id: I11fe59b4ab32e13d6dad246f4e6c56951e051181

public/system_server.te

@@ -4,6 +4,9 @@
 #
 type system_server, domain, domain_deprecated, mlstrustedsubject;
 
+# Attributes for passthrough hals
+typeattribute system_server hal_light;
+
 # For art.
 allow system_server dalvikcache_data_file:dir r_dir_perms;
 allow system_server dalvikcache_data_file:file { r_file_perms execute };