ARM: dts: bcm2711: Enable HWRNG support

This enables hardware random number generator support for the BCM2711
on the Raspberry Pi 4 board.

Signed-off-by: Stephen Brennan <stephen@brennan.io>
Acked-by: Stefan Wahren <wahrenst@gmx.net>
[nsaenzjulienne@suse.de: remove unnecessary status="okay"]
Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>