add missing config files

target/linux/ar7-2.4/config/default

target/linux/aruba-2.6/config/default

target/linux/atheros-2.6/config/default

target/linux/au1000-2.6/config/default

target/linux/brcm-2.4/config/default

target/linux/brcm-2.6/config/default

target/linux/brcm47xx-2.6/config/default

target/linux/brcm63xx-2.6/config/default

target/linux/ixp4xx-2.6/config/default

target/linux/magicbox-2.6/config/default

target/linux/pxa-2.6/config/default

target/linux/rb532-2.6/config/default

target/linux/rdc-2.6/config/default

target/linux/sibyte-2.6/config/default

target/linux/uml-2.6/config/default

target/linux/x86-2.6/config/default