ARM: dts: bcm2711: Add the CEC interrupt controller

The CEC and hotplug interrupts go through an interrupt controller shared
between the two HDMI controllers.

Let's add that interrupt controller and the interrupts for both HDMI
controllers

Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Link: https://lore.kernel.org/r/20210111142309.193441-16-maxime@cerno.tech