rt5350: added pcm interface in .dtsi

Added the missing audio pcm interface in the .dtsi file for the rt5350
device. The update has been verified from the data get from the datasheet
and is very similar to the mt7620a.dtsi

Signed-off-by: Giuseppe Lippolis <giu.lippolis@gmail.com>

target/linux/ramips/dts/rt5350.dtsi

@@ -229,6 +229,19 @@
 			interrupts = <7>;
 		};
 
+		pcm: pcm@2000 {
+			compatible = "ralink,rt5350-pcm";
+			reg = <0x2000 0x800>;
+
+			resets = <&rstctrl 11>;
+			reset-names = "pcm";
+
+			interrupt-parent = <&intc>;
+			interrupts = <4>;
+
+			status = "disabled";
+                };
+
 		gdma: gdma@2800 {
 			compatible = "ralink,rt3883-gdma";
 			reg = <0x2800 0x800>;