arm64: dts: qcom: sm8250-edo: Add hardware keys

Volume Down, GAssist (pdx206 only) and camera keys live on PMIC pins,
with the latter kind being broken for now.. Add these and PON-connected
Volume Up & PWR.

Signed-off-by: Konrad Dybcio <konrad.dybcio@somainline.org>
Link: https://lore.kernel.org/r/20210616122708.144770-1-konrad.dybcio@somainline.org


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