dvb_usb_v2 [RFC] use delayed work.
The problem with an ordinary work queue it executes immediately.
changes made
1. Three extra states added DVB_USB_STATE_PROBE, DVB_USB_STATE_COLD
and DVB_USB_STATE_WARM.
2. Initialise of priv moved to probe this shouldn't really be done in the
work queue.
3. The initial delay 200ms waits for the probe to clear.
4. State DVB_USB_STATE_PROBE checks for interface to be BOUND then calls the
identify_state(possibly extra timeout signals needed if binding fails).
5. The next schedule time now increases to 500ms execution following as before
with state changing accordingly.
6. DVB_USB_STATE_INIT uses the value of 0x7 so clears the other states.
The work queue then dies forever. However, it could continue on as the remote work.
