Keep track of the device status (as returned by the GET_STATUS
request) and allow it to be manipulated by set_selfpowered() as
well as SET_FEATURE/CLEAR_FEATURE (for remote wakeup)
Implement the wakeup() op, which refuses to do anything if the
DEVICE_REMOTE_WAKEUP feature wasn't set by the host. Now this
driver passes USBCV (at least, with gadget zero).
Fix one more locking bug; lockdep is every developer's friend.