dt-bindings: interrupt-controller: brcm,bcm7120-l2-intc: Fix 'brcm,int-fwd-mask' differing type

'brcm,int-fwd-mask' is also defined in brcm,bcm7038-l1-intc.yaml as a
'uint32-array', so unify the type definition.

Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Link: https://lore.kernel.org/r/20230125221423.3058221-1-robh@kernel.org


Signed-off-by: Rob Herring <robh@kernel.org>