ARM: dts: sun7i: Add pin muxing options for clock outputs

This patch adds the clock output pin options on the A20.
The 2 pins can output a configurable clock to be used by
external modules. This is used on the CubieTruck, to supply
a 32768 Hz low power clock to the onboard Wifi+BT module.
Signed-off-by: NChen-Yu Tsai <wens@csie.org>
Signed-off-by: NMaxime Ripard <maxime.ripard@free-electrons.com>

arch/arm/boot/dts/sun7i-a20.dtsi

@@ -389,6 +389,20 @@
 				allwinner,drive = <0>;
 				allwinner,pull = <0>;
 			};
+
+			clk_out_a_pins_a: clk_out_a@0 {
+				allwinner,pins = "PI12";
+				allwinner,function = "clk_out_a";
+				allwinner,drive = <0>;
+				allwinner,pull = <0>;
+			};
+
+			clk_out_b_pins_a: clk_out_b@0 {
+				allwinner,pins = "PI13";
+				allwinner,function = "clk_out_b";
+				allwinner,drive = <0>;
+				allwinner,pull = <0>;
+			};
 		};
 
 		timer@01c20c00 {