soc: qcom: smd-rpm: Create RPM interconnect proxy child device

soc: qcom: smd-rpm: Create RPM interconnect proxy child device

Register a platform device to handle the communication of bus bandwidth
requests with the remote processor. The interconnect proxy device is part
of this remote processor (RPM) hardware. Let's create a icc-smd-rpm proxy
child device to represent the bus throughput functionality that is provided
by the RPM.

Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Georgi Djakov <georgi.djakov@linaro.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>