add osmo_lu_type_names[], osmo_lu_type_name()

Move lupd_names[] from osmo-msc to libosmo-gsm.

Change-Id: Ica25919758ef6cba8348da199b0ae7e0ba628798
diff --git a/include/osmocom/gsm/protocol/gsm_04_08.h b/include/osmocom/gsm/protocol/gsm_04_08.h
index a97225c..791fbd4 100644
--- a/include/osmocom/gsm/protocol/gsm_04_08.h
+++ b/include/osmocom/gsm/protocol/gsm_04_08.h
@@ -1652,6 +1652,10 @@
 #define GSM48_LUPD_IMSI_ATT	0x2
 #define GSM48_LUPD_RESERVED	0x3
 
+extern const struct value_string osmo_lu_type_names[];
+static inline const char *osmo_lu_type_name(uint8_t lu_type)
+{ return get_value_string(osmo_lu_type_names, lu_type); }
+
 /* Table 10.5.4 */
 #define GSM_MI_TYPE_MASK	0x07
 #define GSM_MI_TYPE_NONE	0x00