ALSA: hda - Add digital beep playback switch for STAC/IDT codecs

The digital beep widget may have no mute control, and always enabling
the beep is ofen pretty annoying, especially on laptops.

This patch adds a mixer control "PC Beep Playback Switch" when there
is no mixer amp mute is found, and controls it on software.

Reference: Novell bnc#444572
	https://bugzilla.novell.com/show_bug.cgi?id=444572

Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/pci/hda/hda_beep.c b/sound/pci/hda/hda_beep.c
index 9b77b3e..b1796ae 100644
--- a/sound/pci/hda/hda_beep.c
+++ b/sound/pci/hda/hda_beep.c
@@ -37,6 +37,9 @@
 		container_of(work, struct hda_beep, beep_work);
 	struct hda_codec *codec = beep->codec;
 
+	if (!beep->enabled)
+		return;
+
 	/* generate tone */
 	snd_hda_codec_write_cache(codec, beep->nid, 0,
 			AC_VERB_SET_BEEP_CONTROL, beep->tone);
@@ -115,6 +118,7 @@
 	beep->nid = nid;
 	beep->dev = input_dev;
 	beep->codec = codec;
+	beep->enabled = 1;
 	codec->beep = beep;
 
 	INIT_WORK(&beep->beep_work, &snd_hda_generate_beep);