ARM: dts: imx: Mark IIM as syscon on i.MX51/i.MX53

IIM contains system fuses with information like SoC unique ID
(serial) on i.MX51 and i.MX53. Add "syscon" compatible allowing
simple access.
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/imx51.dtsi

@@ -467,7 +467,7 @@ aipstz2: bridge@83f00000 {
 			};
 
 			iim: efuse@83f98000 {
-				compatible = "fsl,imx51-iim", "fsl,imx27-iim";
+				compatible = "fsl,imx51-iim", "fsl,imx27-iim", "syscon";
 				reg = <0x83f98000 0x4000>;
 				interrupts = <69>;
 				clocks = <&clks IMX5_CLK_IIM_GATE>;

arch/arm/boot/dts/imx53.dtsi

@@ -668,7 +668,7 @@ aipstz2: bridge@63f00000 {
 			};
 
 			iim: efuse@63f98000 {
-				compatible = "fsl,imx53-iim", "fsl,imx27-iim";
+				compatible = "fsl,imx53-iim", "fsl,imx27-iim", "syscon";
 				reg = <0x63f98000 0x4000>;
 				interrupts = <69>;
 				clocks = <&clks IMX5_CLK_IIM_GATE>;