ARM: tegra: add clock source of PMC to device trees

Adding the bindings of the clock source of PMC in DT.

Signed-off-by: Joseph Lo <josephl@nvidia.com>
Signed-off-by: Stephen Warren <swarren@nvidia.com>

arch/arm/boot/dts/tegra20-seaboard.dts

@@ -595,6 +595,19 @@
 		bus-width = <8>;
 	};
 
+	clocks {
+		compatible = "simple-bus";
+		#address-cells = <1>;
+		#size-cells = <0>;
+
+		clk32k_in: clock {
+			compatible = "fixed-clock";
+			reg=<0>;
+			#clock-cells = <0>;
+			clock-frequency = <32768>;
+		};
+	};
+
 	gpio-keys {
 		compatible = "gpio-keys";