clean up handling of some kernel symbols

target/linux/adm5120/router_be/config-2.6.30

target/linux/adm5120/router_be/config-2.6.31

target/linux/adm5120/router_be/config-2.6.32

target/linux/adm5120/router_le/config-2.6.30

target/linux/adm5120/router_le/config-2.6.31

target/linux/adm5120/router_le/config-2.6.32

target/linux/ar7/config-2.6.30

target/linux/ar7/config-2.6.32

target/linux/ar71xx/config-2.6.32

target/linux/atheros/config-2.6.30

target/linux/atheros/config-2.6.31

target/linux/atheros/config-2.6.32

target/linux/brcm47xx/config-2.6.30

target/linux/brcm47xx/config-2.6.31

target/linux/brcm47xx/config-2.6.32

target/linux/brcm63xx/config-2.6.30

target/linux/cobalt/config-2.6.30

target/linux/generic-2.6/config-2.6.25

target/linux/generic-2.6/config-2.6.30

target/linux/generic-2.6/config-2.6.31