ALSA: hda - Fix NULL dereference with CONFIG_SND_DYNAMIC_MINORS=n

Without the dynamic minor assignment, HDMI codec may have less PCM
instances than the number of pins, which eventually leads to Oops.

Reported-by: Stratos Karafotis <stratosk@semaphore.gr>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/pci/hda/patch_hdmi.c

@@ -1781,6 +1781,9 @@ static int generic_hdmi_build_controls(struct hda_codec *codec)
 		struct snd_pcm_chmap *chmap;
 		struct snd_kcontrol *kctl;
 		int i;
+
+		if (!codec->pcm_info[pin_idx].pcm)
+			break;
 		err = snd_pcm_add_chmap_ctls(codec->pcm_info[pin_idx].pcm,
 					     SNDRV_PCM_STREAM_PLAYBACK,
 					     NULL, 0, pin_idx, &chmap);