move yield() usb background in to TinyUSB Core

Author: hathach

cores/arduino/Adafruit_TinyUSB_Core/Adafruit_TinyUSB_Core.cpp

@@ -130,4 +130,17 @@ void Adafruit_TinyUSB_Core_touch1200(void)
   initiateReset(250);
 }
 
+
+extern  "C"
+{
+
+void yield(void)
+
+{
+  tud_task();
+  tud_cdc_write_flush();
+}
+
+}
+
 #endif // USE_TINYUSB

cores/arduino/hooks.c

@@ -29,16 +29,7 @@ static void __empty() {
 	// Empty
 }
 
-#ifdef USE_TINYUSB
-#include "tusb.h"
-void yield(void)
-{
-  tud_task();
-  tud_cdc_write_flush();
-}
-#else
 void yield(void) __attribute__ ((weak, alias("__empty")));
-#endif
 
 /**
  * SysTick hook