arm64: dts: qcom: sc7280: Factor gpio.h include to sc7280.dtsi

Though sc7280 itself doesn't need any of the defines in gpio.h, it's
highly likely that the actual boards will use them. Let's add the
include to the sc7280.dtsi file so that boards don't need to do it.

Suggested-by: Konrad Dybcio <konrad.dybcio@somainline.org>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20220125144316.v2.4.I3194c8bdb2ad3212665286fa273710a3c4840e94@changeid