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

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: dc234825997e ("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>