ALSA: hda - Fix parsing pin node 0x21 on ALC259

ALC259 has a widget NID 0x21 for the output pin, but it wasn't handled
properly in alc268_new_analog_output().

Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/pci/hda/patch_realtek.c b/sound/pci/hda/patch_realtek.c
index 3f92def..79cdae3 100644
--- a/sound/pci/hda/patch_realtek.c
+++ b/sound/pci/hda/patch_realtek.c
@@ -12541,6 +12541,7 @@
 		dac = 0x02;
 		break;
 	case 0x15:
+	case 0x21:
 		dac = 0x03;
 		break;
 	default: