riscv: dts: canaan: Add basic device tree for K230 CanMV board

Add initial dts for K230-CanMV powered by Canaan Kendryte K230 SoC,
which has two RISC-V C908 cores, a big core with vector 1.0 extension
and a small core without vector extension.

This patch is basically comes from Linux Kernel [1] and it assumes
u-boot is running on the big core. Additionally, bootctl and reboot nodes
are added to support sysreset [2] and an clk_dummy node is added to
satisfy dependencies for usb [3].

Currently, u-boot is booted by the vendor's u-boot-spl. To meet the
requirements [4][5] of vendor's u-boot-spl for u-boot, a binman node with
mkimage child node is added here, which will compress u-boot.bin with
gzip and generate an image named "uboot" in the file u-boot-gz.img.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/conor/linux.git/log/?h=k230-basic
[2] https://github.com/kendryte/k230_sdk/blob/v1.8/src/big/rt-smart/kernel/bsp/maix3/board/interdrv/sysctl/sysctl_boot/sysctl_boot.c#L67
[3] https://lore.kernel.org/linux-riscv/tencent_AD84B436C2F31108B66B4739D6E306C5E80A@qq.com/
[4] https://github.com/kendryte/k230_sdk/blob/v1.8/src/little/uboot/board/canaan/common/k230_img.c#L306
[5] https://github.com/kendryte/k230_sdk/blob/v1.8/src/little/uboot/board/canaan/common/k230_img.c#L125

Signed-off-by: Junhui Liu <junhui.liu@pigmoral.tech>
Reviewed-by: Leo Yu-Chi Liang <ycliang@andestech.com>
diff --git a/arch/riscv/dts/k230-u-boot.dtsi b/arch/riscv/dts/k230-u-boot.dtsi
new file mode 100644
index 0000000..bb66ad3
--- /dev/null
+++ b/arch/riscv/dts/k230-u-boot.dtsi
@@ -0,0 +1,25 @@
+// SPDX-License-Identifier: GPL-2.0 OR MIT
+/*
+ * Copyright (C) 2025 Junhui Liu <junhui.liu@pigmoral.tech>
+ */
+
+#include <linux/stringify.h>
+
+/ {
+	binman: binman {
+	};
+};
+
+&binman {
+	mkimage {
+		filename = "u-boot-gz.img";
+		args = "-A", "riscv", "-T", "firmware", "-O", "u-boot",
+			"-C", "gzip", "-n", "uboot",
+			"-a", __stringify(CONFIG_TEXT_BASE),
+			"-e", __stringify(CONFIG_TEXT_BASE);
+		blob {
+			filename = "u-boot.bin";
+			compress = "gzip";
+		};
+	};
+};