stats: add BTS index to IPA RSL TCP stats name

With this change, the new TCP stat names more closely
resemble existing RSL related stat names.

Change-Id: If7ae7f0e75de37e2e52a8ed724c861f57d0da574
diff --git a/src/input/ipaccess.c b/src/input/ipaccess.c
index b410a7e..8dc1008 100644
--- a/src/input/ipaccess.c
+++ b/src/input/ipaccess.c
@@ -296,6 +296,7 @@
 			struct e1inp_ts *ts;
 			struct osmo_fd *newbfd;
 			struct e1inp_line *new_line;
+			char tcp_stat_name[32];
 
 			sign_link =
 				line->ops->sign_link_up(&unit_data, line,
@@ -342,9 +343,9 @@
 				     "could not register FD\n");
 				goto err;
 			}
-			char stat_name[16];
-			snprintf(stat_name, sizeof(stat_name), "ipa-rsl-%u", unit_data.trx_id);
-			osmo_stats_tcp_osmo_fd_register(newbfd, stat_name);
+			snprintf(tcp_stat_name, sizeof(tcp_stat_name), "bts.%u.ipa-rsl.%u",
+				unit_data.bts_id, unit_data.trx_id);
+			osmo_stats_tcp_osmo_fd_register(newbfd, tcp_stat_name);
 
 			e1i_ts = ipaccess_line_ts(newbfd, new_line);
 			ipaccess_bsc_keepalive_fsm_alloc(e1i_ts, newbfd, "rsl_bsc_to_bts");