arm64: dts: qcom: sc7280: Define CPU topology

sc7280 has 8 big.LITTLE CPUs setup with DynamIQ, so all cores are
within the same CPU cluster. Add cpu-map to define the CPU topology.

Signed-off-by: Rajendra Nayak <rnayak@codeaurora.org>
Reviewed-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/1629887818-28489-1-git-send-email-rnayak@codeaurora.org