HO: lchan: store last seen measurement report nr, tweak log

Handover decision 2 will also store the last seen mr nr for neighbor cell
measurements and hence can tell whether a neighbor's measurement is outdated.

Change-Id: Ic1148364597f91b5a55666c80c758b61fa56f582
diff --git a/include/osmocom/bsc/gsm_data.h b/include/osmocom/bsc/gsm_data.h
index 77fda00..65fb32b 100644
--- a/include/osmocom/bsc/gsm_data.h
+++ b/include/osmocom/bsc/gsm_data.h
@@ -422,6 +422,7 @@
 	struct gsm_meas_rep meas_rep[MAX_MEAS_REP];
 	int meas_rep_idx;
 	int meas_rep_count;
+	uint8_t meas_rep_last_seen_nr;
 
 	/* GSM Random Access data */
 	struct gsm48_req_ref *rqd_ref;