spi: spi-imx: Add check for spi_imx_setupxfer()

Add check for the return value of spi_imx_setupxfer().
spi_imx->rx and spi_imx->tx function pointer can be NULL when
spi_imx_setupxfer() return error, and make NULL pointer dereference.

 Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
 Call trace:
  0x0
  spi_imx_pio_transfer+0x50/0xd8
  spi_imx_transfer_one+0x18c/0x858
  spi_transfer_one_message+0x43c/0x790
  __spi_pump_transfer_message+0x238/0x5d4
  __spi_sync+0x2b0/0x454
  spi_write_then_read+0x11c/0x200

Signed-off-by: Tamura Dai <[email protected]>
Reviewed-by: Carlos Song <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Mark Brown <[email protected]>

Author: TMR5454

drivers/spi/spi-imx.c

@@ -1695,9 +1695,12 @@ static int spi_imx_transfer_one(struct spi_controller *controller,
 				struct spi_device *spi,
 				struct spi_transfer *transfer)
 {
+	int ret;
 	struct spi_imx_data *spi_imx = spi_controller_get_devdata(spi->controller);
 
-	spi_imx_setupxfer(spi, transfer);
+	ret = spi_imx_setupxfer(spi, transfer);
+	if (ret < 0)
+		return ret;
 	transfer->effective_speed_hz = spi_imx->spi_bus_clk;
 
 	/* flush rxfifo before transfer */