MIPS: lantiq: implement support for FALCON soc

Adds support for the FALCON SoC. This SoC is from the FTTH/GPON SoC family.

Signed-off-by: Thomas Langer <thomas.langer@lantiq.com>
Signed-off-by: John Crispin <blogic@openwrt.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/3814/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>