arm: bcmbca: add bcm63158 SoC support under CONFIG_ARCH_BCMBCA

BCM63158 is a Broadcom B53 based DSL Gateway SoC. It is part of the
BCA (Broadband Carrier Access origin) chipset family. Like other
Broadband SoC, this patch adds it under CONFIG_BCM63158 chip
config and CONFIG_ARCH_BCMBCA platform config.

This initial support includes a bare-bone implementation and dts with
CPU subsystem, memory and ARM PL011 uart. This SoC is supported in the
linux-next git repository so the dts and dtsi files are copied from
linux.

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

Signed-off-by: William Zhang <william.zhang@broadcom.com>
Reviewed-by: Philippe Reynes <philippe.reynes@softathome.com>