arm64: dts: imx8mn: Enable GPU

The i.MX8M-Nano features a GC7000. The Etnaviv driver detects it as:

    etnaviv-gpu 38000000.gpu: model: GC7000, revision: 6203

Signed-off-by: Adam Ford <aford173@gmail.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm64/boot/dts/freescale/imx8mn.dtsi

@@ -1116,6 +1116,32 @@
 			status = "disabled";
 		};
 
+		gpu: gpu@38000000 {
+			compatible = "vivante,gc";
+			reg = <0x38000000 0x8000>;
+			interrupts = <GIC_SPI 3 IRQ_TYPE_LEVEL_HIGH>;
+			clocks = <&clk IMX8MN_CLK_GPU_AHB>,
+				<&clk IMX8MN_CLK_GPU_BUS_ROOT>,
+				<&clk IMX8MN_CLK_GPU_CORE_ROOT>,
+				<&clk IMX8MN_CLK_GPU_SHADER>;
+			clock-names = "reg", "bus", "core", "shader";
+			assigned-clocks = <&clk IMX8MN_CLK_GPU_CORE>,
+					  <&clk IMX8MN_CLK_GPU_SHADER>,
+					  <&clk IMX8MN_CLK_GPU_AXI>,
+					  <&clk IMX8MN_CLK_GPU_AHB>,
+					  <&clk IMX8MN_GPU_PLL>;
+			assigned-clock-parents = <&clk IMX8MN_GPU_PLL_OUT>,
+						  <&clk IMX8MN_GPU_PLL_OUT>,
+						  <&clk IMX8MN_SYS_PLL1_800M>,
+						  <&clk IMX8MN_SYS_PLL1_800M>;
+			assigned-clock-rates = <400000000>,
+					       <400000000>,
+					       <800000000>,
+					       <400000000>,
+					       <1200000000>;
+			power-domains = <&pgc_gpumix>;
+		};
+
 		gic: interrupt-controller@38800000 {
 			compatible = "arm,gic-v3";
 			reg = <0x38800000 0x10000>,