ARM: at91: sama5d3: add the missing property

If without the MICBIAS routing, the record don't work.
Add the missing MICBIAS routing to let record from mic working.
Signed-off-by: Bo Shen <voice.shen@atmel.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>

arch/arm/boot/dts/sama5d3xmb.dtsi

@@ -166,6 +166,7 @@ sound {
 			"Headphone Jack", "HPOUTR",
 			"IN2L", "Line In Jack",
 			"IN2R", "Line In Jack",
+			"MICBIAS", "IN1L",
 			"IN1L", "Mic";
 
 		atmel,ssc-controller = <&ssc0>;