dt-bindings: interrupt-controller: Fix loongson,parent_int_map property schema

'loongson,parent_int_map' is an array, but the schema is defining a
matrix resulting in the follow warnings:

Documentation/devicetree/bindings/interrupt-controller/loongson,liointc.example.dt.yaml:
  interrupt-controller@3ff01400: loongson,parent_int_map:0: [4043309055] is too short
Documentation/devicetree/bindings/interrupt-controller/loongson,liointc.example.dt.yaml:
  interrupt-controller@3ff01400: loongson,parent_int_map:1: [251658240] is too short
Documentation/devicetree/bindings/interrupt-controller/loongson,liointc.example.dt.yaml:
  interrupt-controller@3ff01400: loongson,parent_int_map:2: [0] is too short
Documentation/devicetree/bindings/interrupt-controller/loongson,liointc.example.dt.yaml:
  interrupt-controller@3ff01400: loongson,parent_int_map:3: [0] is too short

The correct way to define an array is a list in 'items' and/or a size
defined by 'minItems' and 'maxItems'.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: Marc Zyngier <maz@kernel.org>
Signed-off-by: Rob Herring <robh@kernel.org>