ARM64: dts: bcm6858: Add BCMBCA peripherals

ARM64: dts: bcm6858: 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. ARM64 SoCs have additional
peripherals at 0xff858000. Extend the peripheral window range
to 0x400000 and add the DMA controller at offset 0x59000.

Add the watchdog, GPIO blocks, RNG, LED, second UART and DMA
blocks for the BCM6858 based on the vendor files 6858_map_part.h
and 6858_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-v3-11-86f97ab4326f@linaro.org
Signed-off-by: Florian Fainelli <florian.fainelli@broadcom.com>