spi: spi-fsl-dspi: Fix lockup if device is shutdown during SPI transfer

During shutdown, the driver should unregister the SPI controller
and stop the hardware.  Otherwise the dspi_transfer_one_message() could
wait on completion infinitely.

Additionally, calling spi_unregister_controller() first in device
shutdown reverse-matches the probe function, where SPI controller is
registered at the end.

Fixes: dc23482 ("spi: spi-fsl-dspi: Adding shutdown hook")
Reported-by: Vladimir Oltean <olteanv@gmail.com>
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Tested-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20200622110543.5035-2-krzk@kernel.org
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-fsl-dspi.c

@@ -1452,20 +1452,7 @@ static int dspi_remove(struct platform_device *pdev)
 
 static void dspi_shutdown(struct platform_device *pdev)
 {
-	struct spi_controller *ctlr = platform_get_drvdata(pdev);
-	struct fsl_dspi *dspi = spi_controller_get_devdata(ctlr);
-
-	/* Disable RX and TX */
-	regmap_update_bits(dspi->regmap, SPI_MCR,
-			   SPI_MCR_DIS_TXF | SPI_MCR_DIS_RXF,
-			   SPI_MCR_DIS_TXF | SPI_MCR_DIS_RXF);
-
-	/* Stop Running */
-	regmap_update_bits(dspi->regmap, SPI_MCR, SPI_MCR_HALT, SPI_MCR_HALT);
-
-	dspi_release_dma(dspi);
-	clk_disable_unprepare(dspi->clk);
-	spi_unregister_controller(dspi->ctlr);
+	dspi_remove(pdev);
 }
 
 static struct platform_driver fsl_dspi_driver = {