mmc: atmel-mci: fix incorrect setting of host->data to NULL

Setting host->data to NULL is incorrect sequence in STATE_SENDING_STOP
state of FSM: This early setting leads to the skip of dma_unmap_sg()
in atmci_dma_cleanup() which is a bug.

Idea taken from dw_mmc by Seungwon Jeon.
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Seungwon Jeon <tgih.jun@samsung.com>
Acked-by: Ludovic Desroches <ludovic.desroches@atmel.com>
Signed-off-by: Chris Ball <cjb@laptop.org>

drivers/mmc/host/atmel-mci.c

@@ -1685,7 +1685,6 @@ static void atmci_tasklet_func(unsigned long priv)
 
 			dev_dbg(&host->pdev->dev, "FSM: cmd ready\n");
 			host->cmd = NULL;
-			host->data = NULL;
 			data->bytes_xfered = data->blocks * data->blksz;
 			data->error = 0;
 			atmci_command_complete(host, mrq->stop);
@@ -1699,6 +1698,7 @@ static void atmci_tasklet_func(unsigned long priv)
 				atmci_writel(host, ATMCI_IER, ATMCI_NOTBUSY);
 				state = STATE_WAITING_NOTBUSY;
 			}
+			host->data = NULL;
 			break;
 
 		case STATE_END_REQUEST: