arm64: dts: qcom: sm8250: add pinctrl for SPI using GPIO as a CS

GENI SPI controller shows several issues if it manages the CS on its own
(see 37dd4b77

 ("arm64: dts: qcom: sc7180: Provide pinconf for SPI to
use GPIO for CS")) for the details. Provide pinctrl entries for SPI
controllers using the same CS pin but in GPIO mode.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/20210210133458.1201066-4-dmitry.baryshkov@linaro.org
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>