arm64: dts: rockchip: Switch RK3399-Gru DP to SPDIF output

Commit b18c6c3c ("ASoC: rockchip: cdn-dp sound output use spdif")
switched the platform to SPDIF, but we didn't fix up the device tree.

Drop the pinctrl settings, because the 'spdif_bus' pins are either:
 * unused (on kevin, bob), so the settings is ~harmless
 * used by a different function (on scarlet), which causes probe
   failures (!!)

Fixes: b18c6c3c ("ASoC: rockchip: cdn-dp sound output use spdif")
Signed-off-by: Brian Norris <briannorris@chromium.org>
Reviewed-by: Chen-Yu Tsai <wenst@chromium.org>
Link: https://lore.kernel.org/r/20220114150129.v2.1.I46f64b00508d9dff34abe1c3e8d2defdab4ea1e5@changeidSigned-off-by: Heiko Stuebner <heiko@sntech.de>

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

@@ -286,7 +286,7 @@ max98357a: max98357a {
 
 	sound: sound {
 		compatible = "rockchip,rk3399-gru-sound";
-		rockchip,cpu = <&i2s0 &i2s2>;
+		rockchip,cpu = <&i2s0 &spdif>;
 	};
 };
 
@@ -437,10 +437,6 @@ &i2s0 {
 	status = "okay";
 };
 
-&i2s2 {
-	status = "okay";
-};
-
 &io_domains {
 	status = "okay";
 
@@ -537,6 +533,17 @@ &sdmmc {
 	vqmmc-supply = <&ppvar_sd_card_io>;
 };
 
+&spdif {
+	status = "okay";
+
+	/*
+	 * SPDIF is routed internally to DP; we either don't use these pins, or
+	 * mux them to something else.
+	 */
+	/delete-property/ pinctrl-0;
+	/delete-property/ pinctrl-names;
+};
+
 &spi1 {
 	status = "okay";