arm: ls1021atwr: Convert to driver model and enable serial support

Convert ls1021atwr_nor to driver model support. As a start, enable
ns16550 serial port driver.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Acked-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/arm/dts/ls1021a-twr.dts b/arch/arm/dts/ls1021a-twr.dts
index 6ccd332..aead13f 100644
--- a/arch/arm/dts/ls1021a-twr.dts
+++ b/arch/arm/dts/ls1021a-twr.dts
@@ -19,6 +19,10 @@
 		spi0 = &qspi;
 		spi1 = &dspi1;
 	};
+
+	chosen {
+		stdout-path = &uart0;
+	};
 };
 
 &qspi {