spi: imx: fix ERR009165

Change to XCH mode even in dma mode, please refer to the below
errata:
https://www.nxp.com/docs/en/errata/IMX6DQCE.pdf

Signed-off-by: Robin Gong <[e-mail]>
Reviewed-by: Lucas Stach <[e-mail]>
Acked-by: Mark Brown <[e-mail]>
Signed-off-by: Shawn Guo <[e-mail]>

drivers/spi/spi-imx.c

···
 	ctrl |= mx51_ecspi_clkdiv(spi_imx, spi_imx->spi_bus_clk, &clk);
 	spi_imx->spi_bus_clk = clk;
 
-	if (spi_imx->usedma)
-		ctrl |= MX51_ECSPI_CTRL_SMC;
+	/* ERR009165: work in XHC mode as PIO */
+	ctrl &= ~MX51_ECSPI_CTRL_SMC;
 
 	writel(ctrl, spi_imx->base + MX51_ECSPI_CTRL);
 
···
 	 * and enable DMA request.
 	 */
 	writel(MX51_ECSPI_DMA_RX_WML(spi_imx->wml - 1) |
-		MX51_ECSPI_DMA_TX_WML(spi_imx->wml) |
+		MX51_ECSPI_DMA_TX_WML(0) |
 		MX51_ECSPI_DMA_RXT_WML(spi_imx->wml) |
 		MX51_ECSPI_DMA_TEDEN | MX51_ECSPI_DMA_RXDEN |
 		MX51_ECSPI_DMA_RXTDEN, spi_imx->base + MX51_ECSPI_DMA);
···
 			     struct spi_master *master)
 {
 	int ret;
-
-	/* use pio mode for i.mx6dl chip TKT238285 */
-	if (of_machine_is_compatible("fsl,imx6dl"))
-		return 0;
 
 	spi_imx->wml = spi_imx->devtype_data->fifo_size / 2;