ALSA: control - add the missing prev_lops2 initialization

As static analysis reported, the prev_lops2 should contain
the previous lops2 pointer in snd_ctl_disconnect_layer().

Link: https://lore.kernel.org/alsa-devel/96e9bd5c-c8db-0db8-b393-fbf4a047dc80@canonical.com/
Fixes: 3f0638a033 ("ALSA: control - add layer registration routines")
Signed-off-by: Jaroslav Kysela <perex@perex.cz>
Link: https://lore.kernel.org/r/20210331180702.663489-1-perex@perex.cz
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/core/control.c

@@ -2074,7 +2074,7 @@ void snd_ctl_disconnect_layer(struct snd_ctl_layer_ops *lops)
 	struct snd_ctl_layer_ops *lops2, *prev_lops2;
 
 	down_write(&snd_ctl_layer_rwsem);
-	for (lops2 = snd_ctl_layer, prev_lops2 = NULL; lops2; lops2 = lops2->next)
+	for (lops2 = snd_ctl_layer, prev_lops2 = NULL; lops2; lops2 = lops2->next) {
 		if (lops2 == lops) {
 			if (!prev_lops2)
 				snd_ctl_layer = lops->next;
@@ -2082,6 +2082,8 @@ void snd_ctl_disconnect_layer(struct snd_ctl_layer_ops *lops)
 				prev_lops2->next = lops->next;
 			break;
 		}
+		prev_lops2 = lops2;
+	}
 	up_write(&snd_ctl_layer_rwsem);
 }
 EXPORT_SYMBOL_GPL(snd_ctl_disconnect_layer);