msmnile_au: defconfig: Enable the l3mdev config

This change enable the kernel config to
allow route add support to local table from driver.
l3mdev feature allow driver to configure route using table
id.with this config driver is additing route to local table
for E2E data transfer.

Change-Id: Ie3cd358950268e90b5c6b65b80e1a9192a624dfd
Signed-off-by: Lakshit Tyagi <ltyagi@codeaurora.org>