Set right attributes on tracing folder

Since splitting tracefs out from debugfs, we now need to set the
attributes explicitly on tracing folder.

Test: Run adb shell atrace -c -b 16000 -t 5 gfx
Bug: 34197733
Change-Id: If2a962332b6d1ec227e289bdf952213756e26186

rootdir/init.rc

@@ -312,6 +312,7 @@ on post-fs
     # Make sure /sys/kernel/debug (if present) is labeled properly
     # Note that tracefs may be mounted under debug, so we need to cross filesystems
     restorecon --recursive --cross-filesystems /sys/kernel/debug
+    chmod 0755 /sys/kernel/debug/tracing
 
     # We chown/chmod /cache again so because mount is run as root + defaults
     chown system cache /cache