ASoC: bf5xx-ac97: Remove unused extern declaration

The blackfin ac97 driver never defines nor uses a global ac97 struct. So remove
the extern declaration for it.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Mark Brown <broonie@linaro.org>

sound/soc/blackfin/bf5xx-ac97.h

@@ -9,7 +9,6 @@
 #ifndef _BF5XX_AC97_H
 #define _BF5XX_AC97_H
 
-extern struct snd_ac97 *ac97;
 /* Frame format in memory, only support stereo currently */
 struct ac97_frame {
 	u16 ac97_tag;		/* slot 0 */