Everything is just converted to returning RQ_END_IO_NONE, and there
should be no functional changes with this patch.

In preparation for allowing the end_io handler to pass ownership back
to the block layer, rather than retain ownership of the request.
Reviewed-by: NKeith Busch <kbusch@kernel.org>
Signed-off-by: NJens Axboe <axboe@kernel.dk>