ARM: dts: at91: usb_a9g20: use stdout-path

Use stdout-path to specify the console and remove the console argument from
the kernel command line.
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>

arch/arm/boot/dts/usb_a9g20_common.dtsi

@@ -11,7 +11,8 @@
 
 / {
 	chosen {
-		bootargs = "mem=64M console=ttyS0,115200 root=/dev/mtdblock5 rw rootfstype=ubifs";
+		bootargs = "mem=64M root=/dev/mtdblock5 rw rootfstype=ubifs";
+		stdout-path = "serial0:115200n8";
 	};
 
 	memory {