ARM: cygnus: Initial support for Broadcom Cygnus SoC

Adds initial support for the Cygnus SoC based on Broadcom’s iProc series.

Reviewed-by: Ray Jui <rjui@broadcom.com>
Reviewed-by: Desmond Liu <desmondl@broadcom.com>
Reviewed-by: JD (Jiandong) Zheng <jdzheng@broadcom.com>
Tested-by: Jonathan Richardson <jonathar@broadcom.com>
Signed-off-by: Scott Branden <sbranden@broadcom.com>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>