init.rc: make last_kmsg readable only by user system and group log

chown /proc/last_kmsg to user system group log during init, and
chmod it to readable only by user and group.

Bug: 6925227
Change-Id: I645b6a2d4fecc01a2bd4b7fa7ed6aae3ef638cb9
diff --git a/rootdir/init.rc b/rootdir/init.rc
index 22e5e0a..c7063b5 100644
--- a/rootdir/init.rc
+++ b/rootdir/init.rc
@@ -150,6 +150,8 @@
     chmod 0440 /proc/kmsg
     chown root system /proc/sysrq-trigger
     chmod 0220 /proc/sysrq-trigger
+    chown system log /proc/last_kmsg
+    chmod 0440 /proc/last_kmsg
 
     # create the lost+found directories, so as to enforce our permissions
     mkdir /cache/lost+found 0770 root root