ARM: dts: r8a7792: Add device node for PRR

Add a device node for the Product Register, which provides SoC product
and revision information.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

arch/arm/boot/dts/r8a7792.dtsi

@@ -120,6 +120,11 @@ IRQ_TYPE_LEVEL_LOW)>,
 				      IRQ_TYPE_LEVEL_LOW)>;
 		};
 
+		prr: chipid@ff000044 {
+			compatible = "renesas,prr";
+			reg = <0 0xff000044 0 4>;
+		};
+
 		sysc: system-controller@e6180000 {
 			compatible = "renesas,r8a7792-sysc";
 			reg = <0 0xe6180000 0 0x0200>;