defconfig: mdm: Enable VLAN filtering using ebtables

Enable CONFIG_BRIDGE_EBT_VLAN to support VLAN filtering
using ebtables. This change is needed to filter out AVBTP
packets sent over VLAN.

Change-Id: Ic789e6cc316482c3cb9481cb4c7100b4e271d67f
Signed-off-by: Chaitanya Pratapa <cpratapa@codeaurora.org>