spi: fsl: Fix GPIO descriptor support

This makes the driver actually support looking up GPIO
descriptor. A coding mistake in the initial descriptor
support patch was that it was failing to turn on the very
feature it was implementing. Mea culpa.

Cc: Christophe Leroy <christophe.leroy@c-s.fr>
Reported-by: Christophe Leroy <christophe.leroy@c-s.fr>
Fixes: 0f0581b2 ("spi: fsl: Convert to use CS GPIO descriptors")
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Tested-by: Christophe Leroy <christophe.leroy@c-s.fr>
Link: https://lore.kernel.org/r/20191128083718.39177-1-linus.walleij@linaro.orgSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-fsl-spi.c

@@ -611,6 +611,7 @@ static struct spi_master * fsl_spi_probe(struct device *dev,
 	master->setup = fsl_spi_setup;
 	master->cleanup = fsl_spi_cleanup;
 	master->transfer_one_message = fsl_spi_do_one_msg;
+	master->use_gpio_descriptors = true;
 
 	mpc8xxx_spi = spi_master_get_devdata(master);
 	mpc8xxx_spi->max_bits_per_word = 32;