arm64: dts: qcom: msm8992: Make the DT an overlay on top of 8994

This saves a good thousand lines of code, perhaps even
more in the long run.

Co-developed-by: Gustave Monce <gustave.monce@outlook.com>
Signed-off-by: Gustave Monce <gustave.monce@outlook.com>
Signed-off-by: Konrad Dybcio <konrad.dybcio@somainline.org>
Link: https://lore.kernel.org/r/20210131013853.55810-5-konrad.dybcio@somainline.org
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>