fix: correct SerialLP3 instance name for LPUART3

Signed-off-by: Aymane Bahssain <[email protected]>

Author: Aymane-ST

cores/arduino/HardwareSerial.cpp

@@ -114,7 +114,7 @@
     void serialEventLP2() __attribute__((weak));
   #endif
   #if defined(HAVE_HWSERIALLP3)
-    HardwareSerial SerialLP2(LPUART3);
+    HardwareSerial SerialLP3(LPUART3);
     void serialEventLP3() __attribute__((weak));
   #endif
 #endif // HAVE_HWSERIALx