gb: add bssgp2_enc_flush_ll encode FLUSH-LL

Change-Id: I76dc3b08a63cfd78c9f7657fb58c2ddfa9b4b7e2
diff --git a/include/osmocom/gprs/gprs_bssgp2.h b/include/osmocom/gprs/gprs_bssgp2.h
index 3b5b6e8..53e76e3 100644
--- a/include/osmocom/gprs/gprs_bssgp2.h
+++ b/include/osmocom/gprs/gprs_bssgp2.h
@@ -59,6 +59,8 @@
 struct msgb *bssgp2_enc_bvc_reset_ack(uint16_t bvci, const struct gprs_ra_id *ra_id, uint16_t cell_id,
 				      const uint8_t *feat_bm, const uint8_t *ext_feat_bm);
 
+struct msgb *bssgp2_enc_flush_ll(uint32_t tlli, uint16_t old_bvci,
+				 const uint16_t *new_bvci, const uint16_t *nsei);
 struct msgb *bssgp2_enc_status(uint8_t cause, const uint16_t *bvci, const struct msgb *orig_msg, uint16_t max_pdu_len);