spi: spi-s3c64xx: Rename S3C64XX_SPI_SLAVE_* to S3C64XX_SPI_CS_*

Rename S3C64XX_SPI_SLAVE_* to S3C64XX_SPI_CS_* to match documentation.

Signed-off-by: Łukasz Stelmach <l.stelmach@samsung.com>
Reviewed-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://lore.kernel.org/r/20201002122243.26849-6-l.stelmach@samsung.com


Signed-off-by: Mark Brown <broonie@kernel.org>