[ALSA] Fix a typo

Modules: AC97 Codec

Fix a typo in the last patch.
Signed-off-by: NTakashi Iwai <tiwai@suse.de>

sound/pci/ac97/ac97_patch.c

@@ -170,7 +170,7 @@ static inline int is_surround_on(ac97_t *ac97)
 
 static inline int is_clfe_on(ac97_t *ac97)
 {
-	return a97->channel_mode >= 2;
+	return ac97->channel_mode >= 2;
 }
 
 static inline int is_shared_linein(ac97_t *ac97)