block: convert to dequeueing model (easy ones)

plat-omap/mailbox, floppy, viocd, mspro_block, i2o_block and
mmc/card/queue are already pretty close to dequeueing model and can be
converted with simple changes.  Convert them.

While at it,

* xen-blkfront: !fs check moved downwards to share dequeue call with
  normal path.

* mspro_block: __blk_end_request(..., blk_rq_cur_byte()) converted to
  __blk_end_request_cur()

* mmc/card/queue: loop of __blk_end_request() converted to
  __blk_end_request_all()

[ Impact: dequeue in-flight request ]

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Jeremy Fitzhardinge <jeremy@xensource.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Alex Dubov <oakad@yahoo.com>
Cc: Markus Lidel <Markus.Lidel@shadowconnect.com>
Cc: Pierre Ossman <drzeus@drzeus.cx>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

drivers/message/i2o/i2o_block.c

@@ -916,8 +916,10 @@ static void i2o_block_request_fn(struct request_queue *q)
 				blk_stop_queue(q);
 				break;
 			}
-		} else
-			__blk_end_request_cur(req, -EIO);
+		} else {
+			blkdev_dequeue_request(req);
+			__blk_end_request_all(req, -EIO);
+		}
 	}
 };