spi: fsl: Fix GPIO descriptor support

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: 0f0581b24bd0 ("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.org
Signed-off-by: Mark Brown <broonie@kernel.org>