ARM: at91/dt: mpa1600: define crytals frequencies

Define Phontech MPA 1600 main and slow crystals frequencies.

Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>

arch/arm/boot/dts/mpa1600.dts

@@ -25,6 +25,14 @@
 			compatible = "atmel,osc", "fixed-clock";
 			clock-frequency = <18432000>;
 		};
+
+		slow_xtal {
+			clock-frequency = <32768>;
+		};
+
+		main_xtal {
+			clock-frequency = <18432000>;
+		};
 	};
 
 	ahb {