Give system_server access to last reboot reason

system_server needs to be able to read the file
last_reboot_reason to see if we need to show
a thermal notification to the user. This change
allows system_server to read, delete, and rename
the file.

Test: Manual
Bug: 30994946
Change-Id: Id73e18768f910c8de0bfc02f1b464e689f4b3955

private/system_server.te

@@ -30,6 +30,10 @@ allow system_server resourcecache_data_file:dir r_dir_perms;
 # ptrace to processes in the same domain for debugging crashes.
 allow system_server self:process ptrace;
 
+# Read and delete last_reboot_reason file
+allow system_server reboot_data_file:file { rename r_file_perms unlink };
+allow system_server reboot_data_file:dir { write search open remove_name };
+
 # Child of the zygote.
 allow system_server zygote:fd use;
 allow system_server zygote:process sigchld;