Free x component of DSS key upon failure to load

(found by Klocwork)

--HG--
extra : convert_revision : 8dd57944c592d5d74680657e437fca8803680bd0

dss.c

@@ -90,6 +90,9 @@ int buf_get_dss_priv_key(buffer* buf, dss_key *key) {
 	key->x = m_malloc(sizeof(mp_int));
 	m_mp_init(key->x);
 	ret = buf_getmpint(buf, key->x);
+	if (ret == DROPBEAR_FAILURE) {
+		m_free(key->x);
+	}
 
 	return ret;
 }