ARM: brcmstb: add infrastructure for ARM-based Broadcom STB SoCs

The BCM7xxx series of Broadcom SoCs are used primarily in set-top boxes.

This patch adds machine support for the ARM-based Broadcom SoCs.

Signed-off-by: Marc Carino <marc.ceeeee@gmail.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
Signed-off-by: Matt Porter <mporter@linaro.org>