ARM: dts: koelsch: Remove unnecessary clock-output-names properties

* Fixed rate and fixed factor clocks do not require an
  clock-output-names property.
* Since 07705583e920fef6 ("clk: shmobile: div6: Make clock-output-names
  optional") Renesas div6 clocks do not require a clock-output-names
  property.

In the above cases there is only one clock output and its name is taken
from that of the clock node.  Accordingly, remove the unnecessary
clock-output-names properties and as necessary update the node names.

Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>

arch/arm/boot/dts/r8a7791-koelsch.dts

@@ -242,11 +242,10 @@
 			  1800000 0>;
 	};
 
-	audio_clock: clock {
+	audio_clock: audio_clock {
 		compatible = "fixed-clock";
 		#clock-cells = <0>;
 		clock-frequency = <11289600>;
-		clock-output-names = "audio_clock";
 	};
 
 	rsnd_ak4643: sound {