move irqhandler to application

tud_isr() must be called by application to forward the irqhandle to the
stack

src/device/dcd.h

@@ -89,7 +89,7 @@ typedef struct TU_ATTR_ALIGNED(4)
 void dcd_init       (uint8_t rhport);
 
 // Interrupt Handler
-void dcd_isr        (uint8_t rhport);
+void dcd_isr        (uint8_t rhport) TU_ATTR_USED;
 
 // Enable device interrupt
 void dcd_int_enable (uint8_t rhport);