arm64: dts: rockchip: Add pinctrl entry for 32k clock on rk3399

On some rk3399 boards GPIO0_A0 is hooked up to a 32 kHz clock.  This can
be used as the source for various clocks in the system.

Add a pinmux so boards can get this pin properly configured.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>

arch/arm64/boot/dts/rockchip/rk3399.dtsi

@@ -1183,6 +1183,12 @@
 			drive-strength = <13>;
 		};
 
+		clock {
+			clk_32k: clk-32k {
+				rockchip,pins = <0 0 RK_FUNC_2 &pcfg_pull_none>;
+			};
+		};
+
 		i2c0 {
 			i2c0_xfer: i2c0-xfer {
 				rockchip,pins =