mmc: sdhci: fix an issue of mixing different types

Fix an issue reported by sparse, since mixed types of parameters are
used on calling dmaengine_prep_slave_sg().

Fixes: 36e1da441fec (mmc: sdhci: add support for using external DMA devices)
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Chunyan Zhang <zhang.chunyan@linaro.org>
Reviewed-by: Nathan Chancellor <natechancellor@gmail.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Link: https://lore.kernel.org/r/20200120033223.897-1-zhang.chunyan@linaro.org
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/host/sdhci.c

@@ -1201,6 +1201,7 @@ static int sdhci_external_dma_setup(struct sdhci_host *host,
 				    struct mmc_command *cmd)
 {
 	int ret, i;
+	enum dma_transfer_direction dir;
 	struct dma_async_tx_descriptor *desc;
 	struct mmc_data *data = cmd->data;
 	struct dma_chan *chan;
@@ -1234,8 +1235,8 @@ static int sdhci_external_dma_setup(struct sdhci_host *host,
 	if (sg_cnt <= 0)
 		return -EINVAL;
 
-	desc = dmaengine_prep_slave_sg(chan, data->sg, data->sg_len,
-				       mmc_get_dma_dir(data),
+	dir = data->flags & MMC_DATA_WRITE ? DMA_MEM_TO_DEV : DMA_DEV_TO_MEM;
+	desc = dmaengine_prep_slave_sg(chan, data->sg, data->sg_len, dir,
 				       DMA_PREP_INTERRUPT | DMA_CTRL_ACK);
 	if (!desc)
 		return -EINVAL;