ALSA: es1688: Add the missed snd_card_free()

snd_es968_pnp_detect() misses a snd_card_free() in a failed path.
Add the missed function call to fix it.

Fixes: a20971b ("ALSA: Merge es1688 and es968 drivers")
Signed-off-by: Chuhong Yuan <hslester96@gmail.com>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20200603092459.1424093-1-hslester96@gmail.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/isa/es1688/es1688.c

@@ -267,8 +267,10 @@ static int snd_es968_pnp_detect(struct pnp_card_link *pcard,
 		return error;
 	}
 	error = snd_es1688_probe(card, dev);
-	if (error < 0)
+	if (error < 0) {
+		snd_card_free(card);
 		return error;
+	}
 	pnp_set_card_drvdata(pcard, card);
 	snd_es968_pnp_is_probed = 1;
 	return 0;