gfhd100: add CONFIG_TUN to allow for VPN support on storage boxes.

b/19163359

Change-Id: I75c0ce47fe5ac99d7dce33015a0d76918a0399a2
diff --git a/arch/mips/configs/bruno_gfhd100b2_defconfig b/arch/mips/configs/bruno_gfhd100b2_defconfig
index 40d4c74..02ca62f 100644
--- a/arch/mips/configs/bruno_gfhd100b2_defconfig
+++ b/arch/mips/configs/bruno_gfhd100b2_defconfig
@@ -97,6 +97,7 @@
 CONFIG_DM_DEBUG=y
 CONFIG_DM_VERITY=y
 CONFIG_NETDEVICES=y
+CONFIG_TUN=y
 CONFIG_USB_PEGASUS=y
 CONFIG_USB_USBNET=y
 # CONFIG_INPUT_MOUSEDEV_PSAUX is not set