[M487] Remove support for uVisor core debug message via STDIO

This is necessary. Otherwise, program will hang in uninitialized STDIO UART because uVisor core doesn't enable it.

Author: ccli8

targets/TARGET_NUVOTON/TARGET_M480/device/startup_M480.c

@@ -427,14 +427,6 @@ void Reset_Handler_2(void)
      */
 #if defined(FEATURE_UVISOR)
     uvisor_init();
-    
-#if defined(TARGET_UVISOR_SUPPORTED) && defined(TARGET_DEBUG)
-    /* Flush debug message emitted by uvisor core */
-    while (! UART_IS_TX_EMPTY((UART_T *) NU_MODBASE(STDIO_UART)));
-    
-    /* In the following, STDIO_UART will be re-initialized by mbed but it would be compatible with uvisor core.
-     * So uvisor core still can emit debug message with the new setting. */
-#endif
 #endif
 
 #if defined(__CC_ARM)