BTS support: nokia/ericcson - use e1inp_ts->lapd

the lapd member has moved from the .driver.dahdi.lapd to the more
generic lapd location inside 'struct e1inp_ts'
diff --git a/openbsc/src/libbsc/bts_ericsson_rbs2000.c b/openbsc/src/libbsc/bts_ericsson_rbs2000.c
index 28e7df4..5c75192 100644
--- a/openbsc/src/libbsc/bts_ericsson_rbs2000.c
+++ b/openbsc/src/libbsc/bts_ericsson_rbs2000.c
@@ -70,9 +70,9 @@
 
 		llist_for_each_entry(link, &ts->sign.sign_links, list) {
 			if (start)
-				lapd_sap_start(ts->driver.dahdi.lapd, link->tei, link->sapi);
+				lapd_sap_start(ts->lapd, link->tei, link->sapi);
 			else
-				lapd_sap_stop(ts->driver.dahdi.lapd, link->tei, link->sapi);
+				lapd_sap_stop(ts->lapd, link->tei, link->sapi);
 		}
 	}
 }