arm64: dts: salvator-x: add 12288000 for sound ADG

Current rcar_sound only has 11289600 (= for 44.1kHz) clock-frequency,
but it needs 12288000 for 48kHz too.
Otherwise, 48kHz based sound can't handle correctly.
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>

arch/arm64/boot/dts/renesas/salvator-x.dtsi

@@ -523,7 +523,7 @@ &rcar_sound {
 
 	/* audio_clkout0/1/2/3 */
 	#clock-cells = <1>;
-	clock-frequency = <11289600>;
+	clock-frequency = <11289600 12288000>;
 
 	status = "okay";