dt-bindings: misc: add property to support non-secure DSP

Add property to set DSP domain as non-secure.

ADSP/MDSP/SDSP are by default secured, where as CDSP can be either be
secured/unsecured.
non-secured Compute DSP would allow users to load unsigned process
and run hexagon instructions, but limiting access to secured hardware
within the DSP.

Based on this flag device nodes for secured and unsecured are created.

Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Jeya R <jeyr@codeaurora.org>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Link: https://lore.kernel.org/r/20220214161002.6831-5-srinivas.kandagatla@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Jeya R

Documentation/devicetree/bindings/misc/qcom,fastrpc.txt

@@ -17,6 +17,11 @@ other tasks.
 	Definition: should specify the dsp domain name this fastrpc
 	corresponds to. must be one of this: "adsp", "mdsp", "sdsp", "cdsp"
 
+- qcom,non-secure-domain:
+	Usage: required
+	Value type: <boolean>
+	Definition: Property to specify that dsp domain is non-secure.
+
 - #address-cells
 	Usage: required
 	Value type: <u32>