ARM: at91/dt: kizbox: define main crystal frequency

Define kizbox board's main crystal frequency.
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>

arch/arm/boot/dts/kizbox.dts

@@ -30,6 +30,10 @@ main_clock: clock@0 {
 			compatible = "atmel,osc", "fixed-clock";
 			clock-frequency = <18432000>;
 		};
+
+		main_xtal {
+			clock-frequency = <18432000>;
+		};
 	};
 
 	ahb {