dt-bindings: interrupt-controller: apple,aic2: New binding for AICv2

This new incompatible revision of the AIC peripheral introduces
multi-die support. This binding is based on apple,aic, but
changes interrupt-cells to add a new die argument.

Also adds a second reg entry to specify the offset of the event
register. Inexplicably, the capability registers allow us to compute
other register offsets, but not this one. This allows us to keep
forward-compatibility with future SoCs that will likely implement
different die counts, thus shifting the event register. Apple also
specify the offset explicitly in their device tree...

Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Hector Martin <marcan@marcan.st>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220309192123.152028-3-marcan@marcan.st