ARM: dts: sun6i: Add external crystals accuracy

The A31 datasheet mandates oscillators accuracy to be within 50ppm. Let's
add that accuracy to their device tree nodes.
Acked-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>

arch/arm/boot/dts/sun6i-a31.dtsi

@@ -216,6 +216,7 @@ osc24M: clk-24M {
 			#clock-cells = <0>;
 			compatible = "fixed-clock";
 			clock-frequency = <24000000>;
+			clock-accuracy = <50000>;
 			clock-output-names = "osc24M";
 		};
 
@@ -223,6 +224,7 @@ osc32k: clk-32k {
 			#clock-cells = <0>;
 			compatible = "fixed-clock";
 			clock-frequency = <32768>;
+			clock-accuracy = <50000>;
 			clock-output-names = "ext_osc32k";
 		};