ramips: set preinit interface to eth0 by default.

This makes any ramips device accessible via ethernet in failsafe mode.

Based on: https://dev.openwrt.org/changeset/36322



Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>
Patchwork: http://patchwork.openwrt.org/patch/3567/


Acked-by: John Crispin <blogic@openwrt.org>

SVN-Revision: 36434