USB: removed some include file to let core compile again

hardware/sam/cores/sam/CDC.cpp

@@ -18,7 +18,6 @@
 
 #include "Platform.h"
 #include "USBAPI.h"
-#include <avr/wdt.h>
 
 #if defined(USBCON)
 #ifdef CDC_ENABLED
@@ -172,4 +171,4 @@ size_t Serial_::write(uint8_t c)
 Serial_ Serial;
 
 #endif
-#endif /* if defined(USBCON) */
+#endif /* if defined(USBCON) */

hardware/sam/cores/sam/Platform.h

@@ -3,10 +3,6 @@
 #define __PLATFORM_H__
 
 #include <inttypes.h>
-#include <avr/pgmspace.h>
-#include <avr/eeprom.h>
-#include <avr/interrupt.h>
-#include <util/delay.h>
 
 typedef unsigned char u8;
 typedef unsigned short u16;