ramips: add mt76x0 node to RT-AC51U device tree

Introduce mt76x0e device tree node in RT-AC51U dts.
Define mt76x0e mtd partition and offset

Signed-off-by: Lorenzo Bianconi <[email protected]>

target/linux/ramips/dts/RT-AC51U.dts

@@ -135,3 +135,14 @@
 		};
 	};
 };
+
+&pcie {
+	status = "okay";
+};
+
+&pcie0 {
+	wifi@0,0 {
+		reg = <0x0000 0 0 0 0>;
+		mediatek,mtd-eeprom = <&factory 0x8000>;
+	};
+};