ARM: bcm: Add missing sentinel to bcm2711_compat[]

commit 781fa0a9 ("ARM: bcm: Add support for BCM2711 SoC")

breaks boot of many other platforms (e.g. OMAP or i.MX6) if
CONFIG_ARCH_BCM2835 is enabled in addition to some multiplatform
config (e.g. omap2plus_defconfig). The symptom is that the OMAP
based board does not show any activity beyond "Starting Kernel ..."
even with earlycon.

Reverting the mentioned commit makes it work again.

The real fix is to add the missing NULL sentinel to the
bcm2711_compat[] variable-length array.

Fixes: 781fa0a9 ("ARM: bcm: Add support for BCM2711 SoC")
Acked-by: Stefan Wahren <wahrenst@gmx.net>
Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>