ath79: add support for Mercury MW4530R v1

Mercury MW4530R is a TP-Link TL-WDR4310 clone.

Specification:

* SOC: Atheros AR9344 (560 MHz)
* RAM: 128 MiB
* Flash: 8192 KiB
* Ethernet: 5 x 10/100/1000 (4 x LAN, 1 x WAN) (AR8327)
* Wireless:
  - 2.4 GHz b/g/n (internal)
  - 5 GHz a/n (AR9580)
* USB: yes, 1 x USB 2.0

Installation:

Flash factory image via OEM web interface.

Signed-off-by: Zhong Jianxin <azuwis@gmail.com>

target/linux/ath79/dts/ar9344_mercury_mw4530r-v1.dts

@@ -0,0 +1,9 @@
+// SPDX-License-Identifier: GPL-2.0-or-later OR MIT
+/dts-v1/;
+
+#include "ar9344_tplink_tl-wdr4300.dtsi"
+
+/ {
+	model = "Mercury MW4530R v1";
+	compatible = "mercury,mw4530r-v1", "qca,ar9344";
+};