arm64: dts: qcom: add sm8250 hdk dts

Add initial HDK865 dts, based on sm8250-mtp, with a few changes.
Notably, regulator configs are changed a bit.

Signed-off-by: Jonathan Marek <jonathan@marek.ca>
Link: https://lore.kernel.org/r/20200609194030.17756-9-jonathan@marek.ca
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>