ARM: at91/dt: sam9263: Fix typo: ac91_clk -> ac97_clk

That clock should be called ac97_clk.
Signed-off-by: NAlexander Stein <alexanders83@web.de>
Signed-off-by: NNicolas Ferre <nicolas.ferre@atmel.com>

arch/arm/boot/dts/at91sam9263.dtsi

@@ -294,7 +294,7 @@
 						reg = <17>;
 					};
 
-					ac91_clk: ac97_clk {
+					ac97_clk: ac97_clk {
 						#clock-cells = <0>;
 						reg = <18>;
 					};