This adds an early exit when the usb interface with the data endpoints
is not activated. This prevents the cdc_ecm_netdev code from attempting
to send the PDU when the USB device is not yet initialized or activated
by a host.
The OUT endpoint of the cdc ecm data endpoint is only expected to
receive data when the alternative interface is activated. Signalling
ready in the init function can cause issues as the endpoints are not yet
enabled in the low level USB peripheral driver.
This commit changes the name of the requests over the control endpoints
to control requests instead of setup requests. This is a terminology fix
to follow the USB specification more closely as technically only the
first stage of a control request is named setup which contains a setup
packet. The whole transfer is a control transfer.
