arm64: dts: qcom: sc7280: Add Herobrine

Herobrine is a Chrome OS board/platform based on the QCA SC7280.
Add a .dtsi for the platform parts and a .dts for the board
specific bits. Currently the .dtsi has everything except the
compatible strings, things will likely get shuffled around in the
future as we learn more about the differences between boards.

Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20211007140854.1.I70615769f27bbaf7e480419d0f660f802b1fea43@changeid