Add GSMTAP_CHANNEL_VOICE to gsmtap_gsm_channel_names[] value_string

In Change-Id If223020933b083fe359a2e8ff5fab1ce64a363d8 we introduced
GSMTAP_CHANNEL_VOICE, but we didn't add it to gsmtap_gsm_channel_names[]

Change-Id: I7ab696d3e0edb13632e048a9e05be03612d3d28c
Related: OS#2557
diff --git a/src/gsmtap_util.c b/src/gsmtap_util.c
index a4fe2d9..40ec4b8 100644
--- a/src/gsmtap_util.c
+++ b/src/gsmtap_util.c
@@ -479,6 +479,7 @@
 	{ GSMTAP_CHANNEL_ACCH | GSMTAP_CHANNEL_SDCCH8, "SACCH/8" },
 	{ GSMTAP_CHANNEL_ACCH | GSMTAP_CHANNEL_TCH_F, "SACCH/F" },
 	{ GSMTAP_CHANNEL_ACCH | GSMTAP_CHANNEL_TCH_H, "SACCH/H" },
+	{ GSMTAP_CHANNEL_VOICE,		"VOICE" },
 	{ 0, NULL }
 };