ALSA: opl3sa2: add ZV port control

Add ZV port control switch.

This patch is done after solution
given in the ALSA bug #2872 report.
The patch resolves the issue.

Signed-off-by: Krzysztof Helt <krzysztof.h1@wp.pl>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/isa/opl3sa2.c b/sound/isa/opl3sa2.c
index ef95279d..0481a55 100644
--- a/sound/isa/opl3sa2.c
+++ b/sound/isa/opl3sa2.c
@@ -481,6 +481,7 @@
 OPL3SA2_SINGLE("Mic Playback Switch", 0, 0x09, 7, 1, 1),
 OPL3SA2_SINGLE_TLV("Mic Playback Volume", 0, 0x09, 0, 31, 1,
 		   db_scale_5bit_12db_max),
+OPL3SA2_SINGLE("ZV Port Switch", 0, 0x02, 0, 1, 0),
 };
 
 static struct snd_kcontrol_new snd_opl3sa2_tone_controls[] = {