hwrng: iproc-rng200: Add BCM2838 support

The HWRNG on the BCM2838 is compatible to iproc-rng200, so add the
support to this driver instead of bcm2835-rng.

Signed-off-by: Stefan Wahren <wahrenst@gmx.net>

hwrng: iproc-rng200: Correct SoC name

The Pi 4 SoC is called BCM2711, not BCM2838.

Fixes: "hwrng: iproc-rng200: Add BCM2838 support"

Signed-off-by: Phil Elwell <phil@raspberrypi.com>