dt-bindings: apple,aic: Fix required item "apple,fiq-index" in affinity description

The required list used "fiq-index" instead of "apple,fiq-index"
described as property and used in the dts. Add the missing "apple,"
prefix.

Fixes: dba07ad1 ("dt-bindings: apple,aic: Add affinity description for per-cpu pseudo-interrupts")
Signed-off-by: Janne Grunau <j@jannau.net>
Acked-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220909135103.98179-2-j@jannau.netSigned-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/interrupt-controller/apple,aic.yaml

@@ -96,7 +96,7 @@ properties:
               Documentation/devicetree/bindings/arm/cpus.yaml).
 
         required:
-          - fiq-index
+          - apple,fiq-index
           - cpus
 
 required: