dt-bindings: misc: fsl,qoriq-mc: remove ref for msi-parent

msi-parent is standard property. Needn't ref to phandle. Add maxItems: 1
for it.

Fix below warning:
  arch/arm64/boot/dts/freescale/fsl-ls1088a-ten64.dtb: fsl-mc@80c000000: msi-parent:0: [16, 0] is too long
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Frank Li <Frank.Li@nxp.com>
Link: https://lore.kernel.org/r/20241007153047.807723-1-Frank.Li@nxp.comSigned-off-by: Rob Herring (Arm) <robh@kernel.org>

Documentation/devicetree/bindings/misc/fsl,qoriq-mc.yaml

@@ -113,7 +113,7 @@ properties:
 
   msi-parent:
     deprecated: true
-    $ref: /schemas/types.yaml#/definitions/phandle
+    maxItems: 1
     description:
       Describes the MSI controller node handling message
       interrupts for the MC. When there is no translation