arm64: dts: qcom: msm8996: Move regulator consumers to db820c

Supplies for the various components in the SoC depends on board layout,
so move the supply definitions to db820c.dtsi instead of carrying them
in the platform dtsi.

Acked-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>