ALSA: Fix card refcount unbalance

There are uncovered cases whether the card refcount introduced by the
commit a0830dbd isn't properly increased or decreased:
- OSS PCM and mixer success paths
- When lookup function gets NULL

This patch fixes these places.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=50251

Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/core/sound.c

@@ -114,7 +114,7 @@ void *snd_lookup_minor_data(unsigned int minor, int type)
 	mreg = snd_minors[minor];
 	if (mreg && mreg->type == type) {
 		private_data = mreg->private_data;
-		if (mreg->card_ptr)
+		if (private_data && mreg->card_ptr)
 			atomic_inc(&mreg->card_ptr->refcount);
 	} else
 		private_data = NULL;