arm64: dts: qcom: sc7180: Fix cpu compatible

"arm,armv8" compatible should only be used for software models. Replace
it with the real cpu type.

Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Reviewed-by: Rajendra Nayak <rnayak@codeaurora.org>
Signed-off-by: Amit Kucheria <amit.kucheria@linaro.org>
Link: https://lore.kernel.org/r/2526d2b2907116d1bb6f7edd194226eb7e24c333.1584516925.git.amit.kucheria@linaro.org


Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>