add cdc_rndis enum & struct
add tusbh_cdc_serial_is_mounted API
test for cdch close driver
add tests for tusbh_cdc_serial_is_mounted
add tusbh_cdc_send, t usbh_cdc_receive
add cdc_serial_app for virtual com demo
add way to calculate the actual byte transferred with ehci
add come callback for cdch
add code for cdc serial demo
update usbh_xfer_isr to take actual byte transferred and correct tests