dory: enable TUN

b/13903494 b/13918738

Change-Id: Ic72d6ddbeabdecce53b28240321123146539f6bb
Signed-off-by: Dmitry Grinberg <dmitrygr@google.com>

arch/arm/configs/dory_defconfig

@@ -79,6 +79,7 @@ CONFIG_IP_MULTIPLE_TABLES=y
 CONFIG_IP_ROUTE_VERBOSE=y
 CONFIG_IP_PNP=y
 CONFIG_IP_PNP_DHCP=y
+CONFIG_TUN=y
 CONFIG_INET_AH=y
 CONFIG_INET_ESP=y
 # CONFIG_INET_XFRM_MODE_BEET is not set