cores/xmc: Rework review comments.

Signed-off-by: MDin <Dinesh.M-EE@infineon.com>

Author: dineshgit411

cores/xmc/Arduino.h

@@ -343,7 +343,7 @@ extern void loop(void);
 } // extern "C"
   // #include "Tone.h"
   // #include "WMath.h"
-  //  #include "Uart.h"
+    #include "Uart.h"
 #endif // __cplusplus
 
 // #include "Print.h"

cores/xmc/main.cpp

@@ -49,7 +49,7 @@ int main(void) {
     setup();
     while (1) {
         loop();
-        //::serialEventRun();
+        ::serialEventRun();
     }
 }