riscv: dts: thead: add BeagleV Ahead board device tree

The BeagleV Ahead single board computer uses the T-Head TH1520 SoC.
Add a minimal device tree to support basic uart/gpio/dmac drivers so
that a user can boot to a basic shell.

Link: https://beagleboard.org/beaglev-aheadReviewed-by: Guo Ren <guoren@kernel.org>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Drew Fustini <dfustini@baylibre.com>
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>

arch/riscv/boot/dts/thead/Makefile

 # SPDX-License-Identifier: GPL-2.0
-dtb-$(CONFIG_ARCH_THEAD) += th1520-lichee-pi-4a.dtb
+dtb-$(CONFIG_ARCH_THEAD) += th1520-lichee-pi-4a.dtb th1520-beaglev-ahead.dtb

arch/riscv/boot/dts/thead/th1520-beaglev-ahead.dts

+// SPDX-License-Identifier: (GPL-2.0 OR MIT)
+/*
+ * Copyright (C) 2023 Jisheng Zhang <jszhang@kernel.org>
+ * Copyright (C) 2023 Drew Fustini <dfustini@baylibre.com>
+ */
+
+/dts-v1/;
+
+#include "th1520.dtsi"
+
+/ {
+	model = "BeagleV Ahead";
+	compatible = "beagle,beaglev-ahead", "thead,th1520";
+
+	aliases {
+		gpio0 = &gpio0;
+		gpio1 = &gpio1;
+		gpio2 = &gpio2;
+		gpio3 = &gpio3;
+		serial0 = &uart0;
+		serial1 = &uart1;
+		serial2 = &uart2;
+		serial3 = &uart3;
+		serial4 = &uart4;
+		serial5 = &uart5;
+	};
+
+	chosen {
+		stdout-path = "serial0:115200n8";
+	};
+
+	memory@0 {
+		device_type = "memory";
+		reg = <0x0  0x00000000  0x1 0x00000000>;
+
+	};
+};
+
+&osc {
+	clock-frequency = <24000000>;
+};
+
+&osc_32k {
+	clock-frequency = <32768>;
+};
+
+&apb_clk {
+	clock-frequency = <62500000>;
+};
+
+&uart_sclk {
+	clock-frequency = <100000000>;
+};
+
+&dmac0 {
+	status = "okay";
+};
+
+&uart0 {
+	status = "okay";
+};