dt-bindings: arm: bcm2835: Add Raspberry Pi Zero 2 W

Add the Raspberry Pi Zero 2 W to DT schema.

Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>