arm64: dts: imx8mm: drop redundant interrupt-parent

There is interrupt-parent = <&gic> in root node, there is no
need set it again in node ddr-pmu@3d800000.
Signed-off-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm64/boot/dts/freescale/imx8mm.dtsi

@@ -896,7 +896,6 @@ ddrc: memory-controller@3d400000 {
 		ddr-pmu@3d800000 {
 			compatible = "fsl,imx8mm-ddr-pmu", "fsl,imx8m-ddr-pmu";
 			reg = <0x3d800000 0x400000>;
-			interrupt-parent = <&gic>;
 			interrupts = <GIC_SPI 98 IRQ_TYPE_LEVEL_HIGH>;
 		};
 	};