arm64: dts: broadcom: Add minimal support for Raspberry Pi 5

The BCM2712 SoC family can be found on Raspberry Pi 5.
Add minimal SoC and board (Rpi5 specific) dts file to be able to
boot from SD card and use console on debug UART.

Signed-off-by: Andrea della Porta <andrea.porta@suse.com>
Reviewed-by: Stefan Wahren <wahrenst@gmx.net>
Link: https://lore.kernel.org/r/874589f6c621036620cca944986e5be7238b4784.1717061147.git.andrea.porta@suse.com


Signed-off-by: Florian Fainelli <florian.fainelli@broadcom.com>