ramips: add missing i2s alias

Signed-off-by: John Crispin <[email protected]>

target/linux/ramips/dts/rt5350.dtsi

@@ -153,7 +153,7 @@
 			status = "disabled";
 		};
 
-		i2s@a00 {
+		i2s: i2s@a00 {
 			compatible = "ralink,rt3352-i2s";
 			reg = <0xa00 0x100>;