arm64: dts: qcom: sm8250: further split of spi pinctrl config

Split "default" device tree nodes into common "data-clk" nodes and "cs"
nodes which might differ from board to board depending on how the slave
chips are wired.

Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://lore.kernel.org/r/20210210133458.1201066-3-dmitry.baryshkov@linaro.org
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>