base-files: remove network preconfig, it collides with ar71xx network...

base-files: remove network preconfig, it collides with ar71xx network firstboot uci-defaults To supply custom network settings, it is better to embed a complete network config file using the files/ overlay, the old image lan preconfig options are also very limited in scope and actually collide with sysupgrade and firstboot hardware detection on at least ar71xx and possibly other targets, therfore drop this facility.

SVN-Revision: 31258