arm64: dts: qcom: msm8996: use standartized naming for spmi node

Following naming convention, rename qcom,spmi@ node to spmi@

Signed-off-by: David Heidelberg <david@ixit.cz>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20211224163107.53708-1-david@ixit.cz