spi: fsl: Fix driver breakage when SPI_CS_HIGH is not set in spi->mode

Commit 766c6b63 ("spi: fix client driver breakages when using GPIO
descriptors") broke fsl spi driver.

As now we fully rely on gpiolib for handling the polarity of
chip selects, the driver shall not alter the GPIO value anymore
when SPI_CS_HIGH is not set in spi->mode.

Fixes: 766c6b63

 ("spi: fix client driver breakages when using GPIO descriptors")
Cc: stable@vger.kernel.org
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Link: https://lore.kernel.org/r/6b51cc2bfbca70d3e9b9da7b7aa4c7a9d793ca0e.1610629002.git.christophe.leroy@csgroup.eu
Signed-off-by: Mark Brown <broonie@kernel.org>