spi: spi-imx: add support for SPI_MOSI_IDLE_LOW mode bit

spi: spi-imx: add support for SPI_MOSI_IDLE_LOW mode bit

By default, the spi-imx controller pulls the mosi line high, whenever it
is idle. This behaviour can be inverted per CS by setting the
corresponding DATA_CTL bit in the config register of the controller.

Also, since the controller mode-bits have to be touched anyways, the
SPI_CPOL and SPI_CPHA are replaced by the combined SPI_MODE_X_MASK flag.

Signed-off-by: Boerge Struempfel <boerge.struempfel@gmail.com>
Link: https://lore.kernel.org/r/20230530141641.1155691-3-boerge.struempfel@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>