arm: bcmbca: introduce the bcmbca architecture and 47622 SOC

This is the initial support for Broadcom's ARM-based 47622 SOC.

In this change, our first SOC is an armv7 platform called 47622. The
initial support includes a bare-bone implementation and dts with ARM
PL011 uart.

The SOC-specific code resides in arch/arm/mach-bcmbca/<soc> and board
related code is in board/broadcom/bcmba.

The u-boot image can be loaded from flash or network to the entry
point address in the memory and boot from there.

Signed-off-by: William Zhang <william.zhang@broadcom.com>
Signed-off-by: Kursad Oney <kursad.oney@broadcom.com>
Signed-off-by: Anand Gore <anand.gore@broadcom.com>
Reviewed-by: Philippe Reynes <philippe.reynes@softathome.com>