gsm0808: Introduce gsm0808_old_bss_to_new_bss_info_att_tlvdef

Introduce TLV attribute definition for "Old BSS to New BSS Information"
container.

Related: SYS#5337
Change-Id: I0e55e947b6fef6dad0cf1a6c16b781bef4cc76c5
diff --git a/include/osmocom/gsm/gsm0808.h b/include/osmocom/gsm/gsm0808.h
index ecb9827..dc3610f 100644
--- a/include/osmocom/gsm/gsm0808.h
+++ b/include/osmocom/gsm/gsm0808.h
@@ -311,6 +311,7 @@
 void gsm0808_prepend_dtap_header(struct msgb *msg, uint8_t link_id);
 
 const struct tlv_definition *gsm0808_att_tlvdef(void);
+extern const struct tlv_definition gsm0808_old_bss_to_new_bss_info_att_tlvdef;
 
 /*! Parse BSSAP TLV structure using \ref tlv_parse */
 #define osmo_bssap_tlv_parse(dec, buf, len) tlv_parse(dec, gsm0808_att_tlvdef(), buf, len, 0, 0)