staging/lustre: remove unused OBD methods

Remove the unused OBD device methods:
    obd_brw()
    obd_cancel()
    obd_cancel_unused()
    obd_change_cbdata()
    obd_create_async()
    obd_enqueue()
    obd_enqueue_rqset()
    obd_extent_calc()
    obd_llog_connect()
    obd_llog_finish()
    obd_llog_init()
    obd_merge_lvb()
    obd_pin()
    obd_pin_observer()
    obd_ping()
    obd_precreate()
    obd_punch()
    obd_punch_rqset()
    obd_sync()
    obd_sync_rqset()
    obd_unpin()
    obd_unpin_observer()

Signed-off-by: John L. Hammond <john.hammond@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>