ACM gadget: fix endianness in notifications

BugLink: http://bugs.launchpad.net/bugs/1677600

commit cdd7928d upstream.

The gadget code exports the bitfield for serial status changes
over the wire in its internal endianness. The fix is to convert
to little endian before sending it over the wire.
Signed-off-by: Oliver Neukum <oneukum@suse.com>
Tested-by: 家瑋 <momo1208@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>

drivers/usb/gadget/function/f_acm.c

@@ -535,13 +535,15 @@ static int acm_notify_serial_state(struct f_acm *acm)
 {
 	struct usb_composite_dev *cdev = acm->port.func.config->cdev;
 	int			status;
+	__le16			serial_state;
 
 	spin_lock(&acm->lock);
 	if (acm->notify_req) {
 		dev_dbg(&cdev->gadget->dev, "acm ttyGS%d serial state %04x\n",
 			acm->port_num, acm->serial_state);
+		serial_state = cpu_to_le16(acm->serial_state);
 		status = acm_cdc_notify(acm, USB_CDC_NOTIFY_SERIAL_STATE,
-				0, &acm->serial_state, sizeof(acm->serial_state));
+				0, &serial_state, sizeof(acm->serial_state));
 	} else {
 		acm->pending = true;
 		status = 0;