Add /data/misc/reboot and reboot_data_file context

Add a file context for keeping track of last reboot reason and label
directory /data/misc/reboot/ for this purpose.

(Cherry picked from commit ca051f6d)

Bug: 30994946
Test: manual: reboot ocmmand, setprop sys.powerctl, SoC thermal mgr
Change-Id: I9569420626b4029a62448b3f729ecbbeafbc3e66

private/file_contexts

@@ -315,6 +315,7 @@
 /data/misc/logd(/.*)?           u:object_r:misc_logd_file:s0
 /data/misc/media(/.*)?          u:object_r:media_data_file:s0
 /data/misc/net(/.*)?            u:object_r:net_data_file:s0
+/data/misc/reboot(/.*)?         u:object_r:reboot_data_file:s0
 /data/misc/recovery(/.*)?       u:object_r:recovery_data_file:s0
 /data/misc/shared_relro(/.*)?   u:object_r:shared_relro_file:s0
 /data/misc/sms(/.*)?            u:object_r:radio_data_file:s0

public/file.te

@@ -167,6 +167,7 @@ type misc_user_data_file, file_type, data_file_type;
 type net_data_file, file_type, data_file_type;
 type nfc_data_file, file_type, data_file_type;
 type radio_data_file, file_type, data_file_type, mlstrustedobject;
+type reboot_data_file, file_type, data_file_type;
 type recovery_data_file, file_type, data_file_type;
 type shared_relro_file, file_type, data_file_type;
 type systemkeys_data_file, file_type, data_file_type;