usb: eth: asix: Build warning fixes for 64-bit

Fix a type mismatch in a printf format string.

Cc: Marek Vasut <marex@denx.de>
Signed-off-by: Thierry Reding <treding@nvidia.com>

drivers/usb/eth/asix.c

@@ -475,7 +475,7 @@ static int asix_send(struct eth_device *eth, void *packet, int length)
 				length + sizeof(packet_len),
 				&actual_len,
 				USB_BULK_SEND_TIMEOUT);
-	debug("Tx: len = %u, actual = %u, err = %d\n",
+	debug("Tx: len = %zu, actual = %u, err = %d\n",
 			length + sizeof(packet_len), actual_len, err);
 
 	return err;