Always include inttypes.h in usb_serial.h

teensy3/usb_serial.h

@@ -31,10 +31,10 @@
 #ifndef USBserial_h_
 #define USBserial_h_
 
-#if (F_CPU >= 20000000) && (defined(USB_SERIAL) || defined(USB_SERIAL_HID))
-
 #include <inttypes.h>
 
+#if (F_CPU >= 20000000) && (defined(USB_SERIAL) || defined(USB_SERIAL_HID))
+
 // C language implementation
 #ifdef __cplusplus
 extern "C" {