fix: UART0 boot pin setup (espressif#9373)

UART0 pins are set by ROM Boot to default values. This must be reflected into Arduino HardwareSerial in order to allow it to correctly detach it and then attach it to something else.

Summary:
UART0 constructor sets default RX/TX pins as done in boot time.

Author: SuGlider

Diff for: cores/esp32/HardwareSerial.cpp

@@ -99,6 +99,8 @@ _eventTask(NULL)
         }
     }
 #endif
+    // do the same as boot time, that will set default UART0 pins RX, TX. 
+    if(uart_nr == 0) uartSetPins(0, SOC_RX0, SOC_TX0, -1, -1);
 }
 
 HardwareSerial::~HardwareSerial()