defconfig: Enable bridging and ebtables
This patch enables bridging and ebtables BROUTING support for
IPv6 tethering on A-Family MSM devices

Change-Id: I4f461e60bbae018497eaf0f083d639f9756e11aa
CRs-Fixed: 504095
Signed-off-by: Harout Hedeshian <harouth@codeaurora.org>