pkg/semtech-loramac: adapt to iolist netdev

pkg/semtech-loramac/contrib/semtech_loramac_radio.c

@@ -136,10 +136,11 @@ uint32_t SX127XGetTimeOnAir(RadioModems_t modem, uint8_t pktLen)
 void SX127XSend(uint8_t *buffer, uint8_t size)
 {
     netdev_t *dev = (netdev_t *)&sx127x;
-    struct iovec vec[1];
-    vec[0].iov_base = buffer;
-    vec[0].iov_len = size;
-    dev->driver->send(dev, vec, 1);
+    iolist_t iol = {
+        .iol_base = buffer,
+        .iol_len = size
+    };
+    dev->driver->send(dev, &iol);
 }
 
 void SX127XSetSleep(void)