Merge pull request #7989 from OpenNuvoton/nuvoton_fix_m2351_stdiouart

M2351: Fix STDIO_UART error

Author: 0xc0170

targets/TARGET_NUVOTON/TARGET_M2351/PeripheralNames.h

@@ -163,7 +163,7 @@ typedef enum {
 #endif
 
     // NOTE: board-specific
-    STDIO_UART  = UART_3
+    STDIO_UART  = UART_0
 
 } UARTName;