arm64: dts: qcom: sm8250: Add SMP2P nodes

SMP2P is used for interrupting and being interrupted about remoteproc
state changes related to the audio, compute and sensor subsystems.

Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Reviewed-by: Vinod Koul <vkoul@kernel.org>
Link: https://lore.kernel.org/r/20200622222747.717306-5-bjorn.andersson@linaro.org
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>