ramips: add support for HiWiFi HC5611

CPU: MediaTek MT7628AN @ 575 MHz
Flash: 16 MB
RAM: 128 MB
Ethernet: 10/100Mbps x 1
Wlan: 300 Mbps
USB: USB 2.0 x 1
LED: red/green x 1
Button: reset x 1

1. Open https://www.hiwifi.wtf/, Get Cloud token and unlock ssh
2. Upload the openwrt firmware to the router via SCP
3. Login the router via SSH
4. Run `mtd -r write path_to_firmware.bin firmware`

I have tested on my device.
- The LED will display RED on power-on, After system start completed, trun GREEN
- Reset button working now. Long press after 5s will reset factory. Short press less 1s will reboot the device
- USB can working under official u-boot

Signed-off-by: Senis John <thank243@gmail.com>

target/linux/ramips/dts/mt7628an_hiwifi_hc5611.dts

@@ -0,0 +1,30 @@
+// SPDX-License-Identifier: GPL-2.0-or-later OR MIT
+
+#include "mt7628an_hiwifi_hc5x61a.dtsi"
+
+/ {
+	compatible = "hiwifi,hc5611", "mediatek,mt7628an-soc";
+	model = "HiWiFi HC5611";
+
+	leds {
+		compatible = "gpio-leds";
+
+		led_system: system {
+			label = "green:system";
+			gpios = <&gpio 11 GPIO_ACTIVE_HIGH>;
+			default-state = "on";
+		};
+
+		internet {
+			label = "red:internet";
+			gpios = <&gpio 6 GPIO_ACTIVE_LOW>;
+		};
+	};
+};
+
+&state_default {
+	gpio {
+		groups = "gpio", "spi cs1", "wdt";
+		function = "gpio";
+	};
+};