Update the device permission of /dev/tun.

Change-Id: Ie8ad60047fc7160997100bd28a0abb439406806a
diff --git a/rootdir/ueventd.rc b/rootdir/ueventd.rc
index 51a4337..438cf0a 100644
--- a/rootdir/ueventd.rc
+++ b/rootdir/ueventd.rc
@@ -70,11 +70,11 @@
 /dev/bus/usb/*            0660   root       usb
 /dev/mtp_usb              0660   root       mtp
 /dev/usb_accessory        0660   root       usb
+/dev/tun                  0660   system     vpn
 
 # CDMA radio interface MUX
 /dev/ts0710mux*           0640   radio      radio
 /dev/ppp                  0660   radio      vpn
-/dev/tun                  0640   vpn        vpn
 
 # sysfs properties
 /sys/devices/virtual/input/input*   enable      0660  root   input