ALSA: hda: fix oopses in snd-hda-intel after digital slave support additions

Many places fail to check if codec has slave_dig_outs entries (the most common
case is not having any entry), leading to various possible oopses in hda_codec
code.
Signed-off-by: Herton Ronaldo Krzesinski <herton@mandriva.com.br>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>

sound/pci/hda/hda_codec.c

@@ -1462,6 +1462,7 @@ static int snd_hda_spdif_default_put(struct snd_kcontrol *kcontrol,
 					  AC_VERB_SET_DIGI_CONVERT_2,
 					  val >> 8);
 
+		if (codec->slave_dig_outs)
 			for (d = codec->slave_dig_outs; *d; d++) {
 				snd_hda_codec_write_cache(codec, *d, 0,
 					  AC_VERB_SET_DIGI_CONVERT_1,
@@ -1507,6 +1508,7 @@ static int snd_hda_spdif_out_switch_put(struct snd_kcontrol *kcontrol,
 					  AC_VERB_SET_DIGI_CONVERT_1,
 					  val & 0xff);
 
+		if (codec->slave_dig_outs)
 			for (d = codec->slave_dig_outs; *d; d++)
 				snd_hda_codec_write_cache(codec, *d, 0,
 					  AC_VERB_SET_DIGI_CONVERT_1,
@@ -1664,6 +1666,7 @@ static int snd_hda_spdif_in_switch_put(struct snd_kcontrol *kcontrol,
 		snd_hda_codec_write_cache(codec, nid, 0,
 					  AC_VERB_SET_DIGI_CONVERT_1, val);
 
+		if (codec->slave_dig_outs)
 			for (d = codec->slave_dig_outs; *d; d++)
 				snd_hda_codec_write_cache(codec, *d, 0,
 					  AC_VERB_SET_DIGI_CONVERT_1, val);
@@ -2617,6 +2620,7 @@ static void setup_dig_out_stream(struct hda_codec *codec, hda_nid_t nid,
 		snd_hda_codec_write(codec, nid, 0, AC_VERB_SET_DIGI_CONVERT_1,
 			    codec->spdif_ctls & ~AC_DIG1_ENABLE & 0xff);
 
+		if (codec->slave_dig_outs)
 			for (d = codec->slave_dig_outs; *d; d++)
 				snd_hda_codec_write(codec, *d, 0,
 				    AC_VERB_SET_DIGI_CONVERT_1,
@@ -2628,6 +2632,7 @@ static void setup_dig_out_stream(struct hda_codec *codec, hda_nid_t nid,
 		snd_hda_codec_write(codec, nid, 0, AC_VERB_SET_DIGI_CONVERT_1,
 				    codec->spdif_ctls & 0xff);
 
+		if (codec->slave_dig_outs)
 			for (d = codec->slave_dig_outs; *d; d++)
 				snd_hda_codec_write(codec, *d, 0,
 				    AC_VERB_SET_DIGI_CONVERT_1,