USB: OHCI: no shortcut for unlinking URBS from a dead controller

When an URB is unlinked from a dead controller, ohci-hcd gives back
the URB with no regard for cleaning up the internal data structures.
This won't play nicely with the upcoming changes to the TD done
list.

Therefore make ohci_urb_dequeue() call finish_unlinks(), which uses
td_done() to do a proper cleanup, rather than calling finish_urb()
directly.  Also, remove the checks that urb_priv is non-NULL; the
driver guarantees that urb_priv will never be NULL for a valid URB.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>