arm64: dts: qcom: msm8998: Fix cpu compatible

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

Signed-off-by: Amit Kucheria <amit.kucheria@linaro.org>
Link: https://lore.kernel.org/r/0535d640e9cd01887b5532f893ce4d61feca6d6d.1583445235.git.amit.kucheria@linaro.org


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