arm64: dts: freescale: Add i.MX8DX dtsi

Add DTSI for i.MX8DX processor. According to 'i.MX 8DualX Industrial
Applications Processors Data Sheet', the GPU and shader use a clock of
372MHz. Therefore, this dtsi includes the imx8dxp.dtsi and changes the
clock accordingly.
Signed-off-by: Hiago De Franco <hiago.franco@toradex.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm64/boot/dts/freescale/imx8dx.dtsi

+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2016 Freescale Semiconductor, Inc.
+ * Copyright 2017-2020 NXP
+ */
+
+/dts-v1/;
+
+#include "imx8dxp.dtsi"
+
+&gpu_3d0 {
+	assigned-clock-rates = <372000000>, <372000000>;
+};