spi: imx: use pio mode for i.mx6dl

For TKT238285 hardware issue which may cause txfifo store data twice can only
be caught on i.mx6dl, we use pio mode instead of DMA mode on i.mx6dl.

Fixes: f62cacc (spi: spi-imx: add DMA support)
Signed-off-by: Robin Gong <b38343@freescale.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Cc: stable@vger.kernel.org

drivers/spi/spi-imx.c

@@ -823,6 +823,10 @@ static int spi_imx_sdma_init(struct device *dev, struct spi_imx_data *spi_imx,
 	struct dma_slave_config slave_config = {};
 	int ret;
 
+	/* use pio mode for i.mx6dl chip TKT238285 */
+	if (of_machine_is_compatible("fsl,imx6dl"))
+		return 0;
+
 	/* Prepare for TX DMA: */
 	master->dma_tx = dma_request_slave_channel(dev, "tx");
 	if (!master->dma_tx) {