manta: fix permissions on brightness

Change brightness permissions from 0666 to 0660.

Change-Id: Ib41a54dab58635af5b8f127f6cc5bce1fd7e48bf
diff --git a/init.manta.rc b/init.manta.rc
index c85780e..4ed65c2 100755
--- a/init.manta.rc
+++ b/init.manta.rc
@@ -30,7 +30,7 @@
     setprop ro.crypto.fuse_sdcard true
 
 # Permissions for backlight
-    chmod 0666 /sys/class/backlight/pwm-backlight.0/brightness
+    chmod 0660 /sys/class/backlight/pwm-backlight.0/brightness
     chown system system /sys/class/backlight/pwm-backlight.0/brightness
 
 # create virtual SD card at /storage/sdcard0, based on the /data/media directory