mmc: dw_mmc: Fix switch from DMA to PIO

When dw_mci_pre_dma_transfer returns failure in some reasons,
dw_mci_submit_data will prepare to switch the PIO mode from DMA.
After switching to PIO mode, DMA(IDMAC in particular) is still
enabled. This makes the corruption in handling interrupt and
the driver lock-up.

Signed-off-by: Seungwon Jeon <[e-mail]>
Acked-by: Will Newton <[e-mail]>
Signed-off-by: Chris Ball <[e-mail]>

drivers/mmc/host/dw_mmc.c

···
 		return -ENODEV;
 
 	sg_len = dw_mci_pre_dma_transfer(host, data, 0);
-	if (sg_len < 0)
+	if (sg_len < 0) {
+		host->dma_ops->stop(host);
 		return sg_len;
+	}
 
 	host->using_dma = 1;