Reorganize kernel configs - target/linux/*/config is now a directory....

Reorganize kernel configs - target/linux/*/config is now a directory. ./config/default will replace the old config and config-diff (format is like config-diff, the full kernel config is no longer kept in the build system) This commit removes all the kernel config stuff, the next one will add the replacement - there's no way to do this atomically with svn.

SVN-Revision: 6337