ASoC: bfin-ac97: Fix prototype error following AC'97 refactoring

As part of the multiplatform refactoring for AC'97 the AC'97 bus ops were
staticised meaning that the prototype (which was never needed) conflicts
with the declaration causing build failures.
Signed-off-by: NMark Brown <broonie@linaro.org>
Acked-by: NLars-Peter Clausen <lars@metafoo.de>

sound/soc/blackfin/bf5xx-ac97.h

@@ -9,7 +9,6 @@
 #ifndef _BF5XX_AC97_H
 #define _BF5XX_AC97_H
 
-extern struct snd_ac97_bus_ops bf5xx_ac97_ops;
 extern struct snd_ac97 *ac97;
 /* Frame format in memory, only support stereo currently */
 struct ac97_frame {