ARM: dts: nxp/imx: limit sk-imx53 supported frequencies

The SK-IMX53 board, bearing i.MX536A CPU, is not stable when running at
1.2 GHz (default iMX53 maximum). The SoC is only rated up to 800 MHz.
Disable 1.2 GHz and 1 GHz frequencies.

Fixes: 0b8576d8 ("ARM: dts: imx: Add support for SK-iMX53 board")
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Fabio Estevam <festevam@gmail.com>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm/boot/dts/nxp/imx/imx53-sk-imx53.dts

@@ -60,6 +60,16 @@ &can1 {
 	status = "okay";
 };
 
+&cpu0 {
+	/* CPU rated to 800 MHz, not the default 1.2GHz. */
+	operating-points = <
+		/* kHz   uV */
+		166666  850000
+		400000  900000
+		800000  1050000
+	>;
+};
+
 &ecspi1 {
 	pinctrl-names = "default";
 	pinctrl-0 = <&pinctrl_ecspi1>;