refractor list_find_previous_item & list_remove_qhd to act on ehci_link_t* instead of ehci_qhd_t*
fully support 1ms, 2ms, 4ms, 8ms for period list (each list has a dummy queue head)
- change period list structure
limit the maximum polling interval to 256 ms
add max_loop static MAX number of iteration for list_find_previous_item
add test for close 256ms polling interrupt
implementing freeRTOS integration
change get_period_frame_list from using lst_idx to hostid (fix bug)
adding polling interval supported for interrupt: 1ms, 2ms, 4ms, 8ms
- add interval_ms to get_period_head function
- add bInterval to qhd_init
- add support for sub-frame (less than 8 micro frames) interval
- add bunch of test for interrupt different intervals
- interrupt source identifying
- for async list process
refractor control_xfer to use insert_qtd_to_qhd
- add test for control xfer interrupt processing
- add code for faking ehci controller async list scheduling & processing
- add prototype for void usbh_isr(pipe_handle_t pipe_hdl, uint8_t class_code);
