arm64: dts: qcom: Switch sc7180-trogdor to control SPI CS via GPIO

arm64: dts: qcom: Switch sc7180-trogdor to control SPI CS via GPIO

As talked about in the patch ("arm64: dts: qcom: sc7180: Provide
pinconf for SPI to use GPIO for CS"), on some boards it makes much
more sense (and is much more efficient) to think of the SPI Chip
Select as a GPIO.  Trogdor is one such board where the SPI parts don't
run in GSI mode and we do a lot of SPI traffic.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Reviewed-by: Akash Asthana <akashast@codeaurora.org>
Link: https://lore.kernel.org/r/20200921142655.v3.2.I3c57d8b6d83d5bdad73a413eea1e249a98d11973@changeid
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>