init.rc: create /data/misc/reboot for storing reboot reason

Create /data/misc/reboot if not already.

Bug: 30994946
Test: manual: reboot command; modified thermal-engine.conf
Change-Id: I66418beba539f76759b44742af7700f26a2c1f87
diff --git a/rootdir/init.rc b/rootdir/init.rc
index 9ab2333..1e5fa50 100644
--- a/rootdir/init.rc
+++ b/rootdir/init.rc
@@ -402,6 +402,7 @@
     mkdir /data/misc/boottrace 0771 system shell
     mkdir /data/misc/update_engine 0700 root root
     mkdir /data/misc/trace 0700 root root
+    mkdir /data/misc/reboot 0700 root root
     # profile file layout
     mkdir /data/misc/profiles 0771 system system
     mkdir /data/misc/profiles/cur 0771 system system