MIPS: Lantiq: Add initial support for Lantiq SoCs

Add initial support for Mips based SoCs made by Lantiq. This series will add
support for the XWAY family.

The series allows booting a minimal system using a initramfs or NOR. Missing
drivers and support for Amazon and GPON family will be provided in a later
series.

[Ralf: Remove some cargo cult programming and fixed formatting.]

Signed-off-by: John Crispin <blogic@openwrt.org>
Signed-off-by: Ralph Hempel <ralph.hempel@lantiq.com>
Signed-off-by: David Daney <ddaney@caviumnetworks.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/2252/
Patchwork: https://patchwork.linux-mips.org/patch/2371/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>