arm64: dts: qcom: msm8996: Use node references in db820c

[ Upstream commit 75b77d6492eb5e582e17618b71f62140faf2de29 ]

Instead of mimicing the structure of the platform, reference nodes by
their label in apq8096-db820c.dtsi. Add labels in msm8996.dtsi where
necessary.

Acked-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Stable-dep-of: 68c4c20848d7 ("arm64: dts: qcom: msm8996: Define UFS UniPro clock limits")
Signed-off-by: Sasha Levin <sashal@kernel.org>