arm64: dts: imx8m: Add ddr-pmu nodes

The same ddr perfomance counter IP from 8qxp is also available on imx8m
series so add it to dts.

Tested with `perf stat` and `memtester` on imx8mm-evk and obtained
plausible results.
Signed-off-by: Leonard Crestez <leonard.crestez@nxp.com>
Acked-by: Frank Li <frank.li@nxp.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

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

@@ -831,5 +831,12 @@ gic: interrupt-controller@38800000 {
 			interrupt-controller;
 			interrupts = <GIC_PPI 9 IRQ_TYPE_LEVEL_HIGH>;
 		};
+
+		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>;
+		};
 	};
 };

arch/arm64/boot/dts/freescale/imx8mq.dtsi

@@ -1051,5 +1051,12 @@ gic: interrupt-controller@38800000 {
 			interrupts = <GIC_PPI 9 IRQ_TYPE_LEVEL_HIGH>;
 			interrupt-parent = <&gic>;
 		};
+
+		ddr-pmu@3d800000 {
+			compatible = "fsl,imx8mq-ddr-pmu", "fsl,imx8m-ddr-pmu";
+			reg = <0x3d800000 0x400000>;
+			interrupt-parent = <&gic>;
+			interrupts = <GIC_SPI 98 IRQ_TYPE_LEVEL_HIGH>;
+		};
 	};
 };