arm64: dts: qcom: msm8916: Add Hexagon PIL node

The Hexagon core on the msm8916 provides services for audio control,
audio output, sensors and the Hexagon SDK. The Hexagon remoteproc node
allows us to boot this core.

Although its part of the core platform its left disabled as it will
crash without the rmtfs QMI service and we do not yet handle crashes
gracefully.

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