ARM: dts: bcm6878: Add BCMBCA peripherals

ARM: dts: bcm6878: Add BCMBCA peripherals

All the BCMBCA SoCs share a set of peripherals at 0xff800000,
albeit at slightly varying memory locations on the bus and
with varying IRQ assignments.

Add the first and second watchdog, GPIO, RNG, LED and
DMA blocks for the BCM6878 based on the vendor files
6878_map_part.h and 6878_intr.h from the "bcmopen-consumer"
code drop.

This SoC has up to 256 possible GPIOs due to having 8
registers with 32 GPIOs in each available.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: William Zhang <william.zhang@broadcom.com>
Link: https://lore.kernel.org/r/20250512-bcmbca-peripherals-arm-v3-5-86f97ab4326f@linaro.org
Signed-off-by: Florian Fainelli <florian.fainelli@broadcom.com>