lapd: Fix compiler warnings in the lapd code

lapd_test.c: In function ‘ms_to_bts_l1_cb’:
lapd_test.c:192:6: warning: variable ‘rc’ set but not used [-Wunused-but-set-variable]
lapd_test.c:199:1: warning: no return statement in function returning non-void [-Wreturn-type]
lapd_test.c: In function ‘main’:
lapd_test.c:355:2: warning: implicit declaration of function ‘osmo_init_logging’ [-Wimplicit-function-declaration]
diff --git a/tests/lapd/lapd_test.c b/tests/lapd/lapd_test.c
index 2dabbc6..acd3cad 100644
--- a/tests/lapd/lapd_test.c
+++ b/tests/lapd/lapd_test.c
@@ -19,6 +19,7 @@
  *
  */
 
+#include <osmocom/core/application.h>
 #include <osmocom/core/logging.h>
 #include <osmocom/gsm/lapdm.h>
 #include <osmocom/gsm/rsl.h>
@@ -196,6 +197,7 @@
 	/* i stuff it into the LAPDm channel of the BTS */
 	rc = send(oph->msg, state->bts);
 	msgb_free(oph->msg);
+	return rc;
 }
 
 static int ms_to_bts_tx_cb(struct msgb *msg, struct lapdm_entity *le, void *_ctx)