ARM: sunxi: dt: Use clocks property instead of clock-frequency for the UARTs

It will be especially useful when we will have the clock definitions in
the device tree.
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Acked-by: Emilio López <emilio@elopez.com.ar>
Tested-by: Emilio López <emilio@elopez.com.ar>

arch/arm/boot/dts/sunxi.dtsi

@@ -142,7 +142,7 @@ uart0: uart@01c28000 {
 			interrupts = <1>;
 			reg-shift = <2>;
 			reg-io-width = <4>;
-			clock-frequency = <24000000>;
+			clocks = <&osc>;
 			status = "disabled";
 		};
 
@@ -152,7 +152,7 @@ uart1: uart@01c28400 {
 			interrupts = <2>;
 			reg-shift = <2>;
 			reg-io-width = <4>;
-			clock-frequency = <24000000>;
+			clocks = <&osc>;
 			status = "disabled";
 		};
 	};