arm64: dts: qcom: msm8916: Update hexagon node

It's necessary to reference the xo clock and cx supply, so specify these
in the node. Also move the Hexagon smd-edge into the hexagon node, to
enable SSR.

As cxo is not yet available we reference the fixed version of cxo for
now, which will work until proper power management is implemented.

Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Andy Gross <andy.gross@linaro.org>