- addd p_qtd_list_tail to qhd structure for easy queue TD

- move control_request from ehci_data to usbh_device_info_pool
- add test for bulk transfer double (2 consecutive xfers)
- use table (array) structure for class driver, currently included
- refractor extract to function insert_qtd_to_qhd
+ init function
+ install_subtask
--> all class driver function must be declared with WEAK

tests/test/host/ehci/test_ehci_pipe.c

@@ -114,6 +114,7 @@ void verify_open_qhd(ehci_qhd_t *p_qhd, uint8_t endpoint_addr, uint16_t max_pack
   //------------- HCD -------------//
   TEST_ASSERT(p_qhd->used);
   TEST_ASSERT_NULL(p_qhd->p_qtd_list_head);
+  TEST_ASSERT_NULL(p_qhd->p_qtd_list_tail);
 }
 
 //--------------------------------------------------------------------+