nios2: 10m50: change to ns16550 uart

Change to ns16550 uart for 10m50 devboard based on a new
Altera release.

Signed-off-by: Thomas Chou <thomas@wytron.com.tw>
Reviewed-by: Tom Rini <trini@konsulko.com>
Acked-by: Simon Glass <sjg@chromium.org>

arch/nios2/dts/10m50_devboard.dts

@@ -262,6 +262,6 @@
 
 	chosen {
 		bootargs = "debug console=ttyS0,115200";
-		stdout-path = &uart_0;
+		stdout-path = &a_16550_uart_0;
 	};
 };