ARM: imx_v6_v7_defconfig: Enable BT_BNEP

This is necessary to support network over bluetooth:

| Sep 11 15:36:33 imx6qdl-variscite-som bluetoothd[281]: kernel lacks bnep-protocol support
| Sep 11 15:36:33 imx6qdl-variscite-som bluetoothd[281]: System does not support network plugin

Reviewed-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Andreas Müller <schnitzeltony@gmail.com>
Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>