ARM: at91/dt: at91sam9g20ek: define crystals frequencies

Define at91sam9g20ek main and slow crystals frequencies.

Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
diff --git a/arch/arm/boot/dts/at91sam9g20ek_common.dtsi b/arch/arm/boot/dts/at91sam9g20ek_common.dtsi
index cb2c010..d291910 100644
--- a/arch/arm/boot/dts/at91sam9g20ek_common.dtsi
+++ b/arch/arm/boot/dts/at91sam9g20ek_common.dtsi
@@ -26,6 +26,14 @@
 			compatible = "atmel,osc", "fixed-clock";
 			clock-frequency = <18432000>;
 		};
+
+		slow_xtal {
+			clock-frequency = <32768>;
+		};
+
+		main_xtal {
+			clock-frequency = <18432000>;
+		};
 	};
 
 	ahb {