Fix LAPD UA msgb memory leak.

Change-Id: Ia4f0606810e00aa6f1779d11893e4acc01976f9a
diff --git a/src/gsm/lapd_core.c b/src/gsm/lapd_core.c
index 1f1ca83..4847626 100644
--- a/src/gsm/lapd_core.c
+++ b/src/gsm/lapd_core.c
@@ -307,6 +307,9 @@
 /* reset to IDLE state */
 void lapd_dl_reset(struct lapd_datalink *dl)
 {
+	LOGP(DLLAPD, LOGL_INFO, "Resetting LAPDm instance\n");
+	/* enter idle state (and remove eventual cont_res) */
+	lapd_dl_newstate(dl, LAPD_STATE_IDLE);
 	/* flush buffer */
 	lapd_dl_flush_tx(dl);
 	lapd_dl_flush_send(dl);