dt-bindings: interrupt-controller: loongson,liointc: Fix dtbs_check warning for interrupt-names

The Loongson-2K0500/2K1000 CPUs have 64 interrupt sources as inputs, and
a route-mapped node handles up to 32 interrupt sources, so two liointc
nodes are defined in dts{i}.

Of course, we have to make sure that the routing outputs ("intx") of the
two nodes do not conflict, i.e. "int0" can only be used as a routing
output for one of them. Therefore, "interrupt-names" should be defined
as "pattern".

In addition, since "interrupt-names" and "interrupts" are one-to-one
correspondence, we pass it to get the corresponding interrupt number in
the driver. Setting it to "required" does not break ABI, because it is
already logically represented as "required".

This fixes dtbs_check warning:

DTC_CHK arch/loongarch/boot/dts/loongson-2k0500-ref.dtb
arch/loongarch/boot/dts/loongson-2k0500-ref.dtb: interrupt-controller@1fe11440: interrupt-names:0: 'int0' was expected
        From schema: Documentation/devicetree/bindings/interrupt-controller/loongson,liointc.yaml
arch/loongarch/boot/dts/loongson-2k0500-ref.dtb: interrupt-controller@1fe11440: Unevaluated properties are not allowed ('interrupt-names' was unexpected)
        From schema: Documentation/devicetree/bindings/interrupt-controller/loongson,liointc.yaml
DTC_CHK arch/loongarch/boot/dts/loongson-2k1000-ref.dtb
arch/loongarch/boot/dts/loongson-2k1000-ref.dtb: interrupt-controller@1fe01440: interrupt-names:0: 'int0' was expected
        From schema: Documentation/devicetree/bindings/interrupt-controller/loongson,liointc.yaml
arch/loongarch/boot/dts/loongson-2k1000-ref.dtb: interrupt-controller@1fe01440: Unevaluated properties are not allowed ('interrupt-names' was unexpected)
        From schema: Documentation/devicetree/bindings/interrupt-controller/loongson,liointc.yaml

Acked-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Binbin Zhou <zhoubinbin@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>