With this commit the DSPI driver on the BK4 board can be used for SPI
transmission managed from user space (via /dev/spidev0.0).

Example usage/testing:
insmod ./spi-fsl-dspi.ko
./spidev_test -D /dev/spidev0.0 -s 3000000 -v -H -b 8 -p "\xCC\x11\x22\x74"
Signed-off-by: Lukasz Majewski <lukma@denx.de>
Signed-off-by: Mark Brown <broonie@kernel.org>