dt-bindings: soc: qcom: cdsprm rpmsg

Documentation for device tree bindings related to CDSPRM and CDSP L3
governor.

Change-Id: Id6f6ec7559c34de68db1503b857093b414000f14
Acked-by: Sreekanth Gande <sgande@qti.qualcomm.com>
Signed-off-by: Tharun Kumar Merugu <mtharu@codeaurora.org>