ALSA: snd_ctl_activate_id(): Fix index look-up

We want to know the offset for the id that was passed to the function, not
the offset of the first id of the control (which is always 0).

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/core/control.c b/sound/core/control.c
index 99aa3aa..bb96a46 100644
--- a/sound/core/control.c
+++ b/sound/core/control.c
@@ -572,7 +572,7 @@
 		ret = -ENOENT;
 		goto unlock;
 	}
-	index_offset = snd_ctl_get_ioff(kctl, &kctl->id);
+	index_offset = snd_ctl_get_ioff(kctl, id);
 	vd = &kctl->vd[index_offset];
 	ret = 0;
 	if (active) {