nrf5x: refactor device control transfer.

- make control transfer as part of usbd. Class driver must use
usbd_control_ API() instead of dcd_ api.
- change the signature of class driver's control_request
- allow control request complete to stall in staus stage
- move control request parser & handling to usbd.

src/device/usbd_pvt.h

@@ -54,15 +54,24 @@ extern tud_desc_set_t const* usbd_desc_set;
 tusb_error_t usbd_init (void);
 void         usbd_task (void* param);
 
+
+// Carry out Data and Status stage of control transfer
+// - If len = 0, it is equivalent to sending status only
+// - If len > wLength : it will be truncated
+bool usbd_control_xfer(uint8_t rhport, tusb_control_request_t const * request, void* buffer, uint16_t len);
+
+// Send STATUS (zero length) packet
+bool usbd_control_status(uint8_t rhport, tusb_control_request_t const * request);
+
+// Stall control endpoint until new setup packet arrived
+void usbd_control_stall(uint8_t rhport);
+
 /*------------------------------------------------------------------*/
-/* Endpoint helper
+/* Helper
  *------------------------------------------------------------------*/
 // helper to parse an pair of In and Out endpoint descriptors. They must be consecutive
 tusb_error_t usbd_open_edpt_pair(uint8_t rhport, tusb_desc_endpoint_t const* p_desc_ep, uint8_t xfer_type, uint8_t* ep_out, uint8_t* ep_in);
 
-/*------------------------------------------------------------------*/
-/* Other Helpers
- *------------------------------------------------------------------*/
 void usbd_defer_func( osal_task_func_t func, void* param, bool in_isr );