dm: sunxi: Add support for serial using driver model

Add a driver for the designware serial UART used on sunxi. This just
redirects to the normal ns16550 driver.

Add a stdout-path to the device tree so that the correct UART is chosen.

Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
diff --git a/arch/arm/dts/sun7i-a20-pcduino3.dts b/arch/arm/dts/sun7i-a20-pcduino3.dts
index 046dfc0..f7cc8e7 100644
--- a/arch/arm/dts/sun7i-a20-pcduino3.dts
+++ b/arch/arm/dts/sun7i-a20-pcduino3.dts
@@ -20,6 +20,10 @@
 	model = "LinkSprite pcDuino3";
 	compatible = "linksprite,pcduino3", "allwinner,sun7i-a20";
 
+	chosen {
+		stdout-path = &uart0;
+	};
+
 	soc@01c00000 {
 		mmc0: mmc@01c0f000 {
 			pinctrl-names = "default";