lantiq: remove 3.18 support

target/linux/lantiq/config-3.18

...antiq/patches-3.18/0001-MIPS-lantiq-add-pcie-driver.patch

...lantiq/patches-3.18/0002-MIPS-lantiq-dtb-image-hack.patch

....18/0003-MIPS-lantiq-handle-vmmc-memory-reservation.patch

...x/lantiq/patches-3.18/0004-MIPS-lantiq-add-atm-hack.patch

...8/0005-MIPS-lantiq-add-reset-controller-api-support.patch

...atches-3.18/0006-MIPS-lantiq-reboot-gphy-on-restart.patch

...patches-3.18/0007-MIPS-lantiq-add-basic-tffs-driver.patch

...tches-3.18/0008-MIPS-lantiq-backport-old-timer-code.patch

...ches-3.18/0009-MIPS-lantiq-command-line-work-around.patch

...antiq/patches-3.18/0010-MIPS-lantiq-export-soc-type.patch

...antiq-add-support-for-xrx200-firmware-depending-on-.patch

...ntiq/patches-3.18/0012-pinctrl-lantiq-fix-up-pinmux.patch

...ches-3.18/0013-MTD-lantiq-xway-fix-invalid-operator.patch

...TD-lantiq-xway-the-latched-command-should-be-persis.patch

...tches-3.18/0015-MTD-lantiq-xway-remove-endless-loop.patch

...TD-lantiq-xway-add-missing-write_buf-and-read_buf-t.patch

.../lantiq/patches-3.18/0017-MTD-xway-fix-nand-locking.patch

...tiq/patches-3.18/0018-MTD-nand-lots-of-xrx200-fixes.patch

...3.18/0020-MTD-lantiq-handle-NO_XIP-on-cfi0001-flash.patch