dt-bindings: arm: renesas: Move 'renesas,prr' binding to its own doc

In preparation to convert board-level bindings to json-schema, move
various misc SoC bindings out to their own file.
Signed-off-by: Rob Herring <robh@kernel.org>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

Documentation/devicetree/bindings/arm/renesas,prr.txt

+Renesas Product Register
+
+Most Renesas ARM SoCs have a Product Register or Boundary Scan ID Register that
+allows to retrieve SoC product and revision information.  If present, a device
+node for this register should be added.
+
+Required properties:
+  - compatible: Must be one of:
+    "renesas,prr"
+    "renesas,bsid"
+  - reg: Base address and length of the register block.
+
+
+Examples
+--------
+
+	prr: chipid@ff000044 {
+		compatible = "renesas,prr";
+		reg = <0 0xff000044 0 4>;
+	};

Documentation/devicetree/bindings/arm/shmobile.txt

@@ -153,21 +153,3 @@ Boards:
     compatible = "renesas,v3msk", "renesas,r8a77970"
   - Wheat (RTP0RC7792ASKB0000JE)
     compatible = "renesas,wheat", "renesas,r8a7792"
-
-
-Most Renesas ARM SoCs have a Product Register or Boundary Scan ID Register that
-allows to retrieve SoC product and revision information.  If present, a device
-node for this register should be added.
-
-Required properties:
-  - compatible: Must be "renesas,prr" or "renesas,bsid"
-  - reg: Base address and length of the register block.
-
-
-Examples
---------
-
-	prr: chipid@ff000044 {
-		compatible = "renesas,prr";
-		reg = <0 0xff000044 0 4>;
-	};