ARM: dts: imx27: Add core voltages

This patch adds core voltages for i.MX27 CPUs. Only 266 and 400 MHz modes
is documented in the datasheet, so we add a 266 MHz frequency for conform this.
Signed-off-by: Alexander Shiyan <shc_work@mail.ru>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>

arch/arm/boot/dts/imx27.dtsi

@@ -57,13 +57,14 @@ cpu {
 			device_type = "cpu";
 			compatible = "arm,arm926ej-s";
 			operating-points = <
-				/* kHz  uV (No regulator support) */
-				133000  0
-				399000  0
+				/* kHz uV */
+				266000 1300000
+				399000 1450000
 			>;
 			clock-latency = <61036>; /* two CLK32 periods */
 			clocks = <&clks 18>;
 			clock-names = "cpu";
+			voltage-tolerance = <5>;
 		};
 	};