usb: gadget: composite: fix req->length in composite_setup()

When USB CV MSC tests are run on f_mass_storage gadget
Bulk Only Mass Storage Reset fails since req->length
is set to USB_BUFSIZ=1024 in composite_setup().

Initialize req->length to zero to fix this.
Signed-off-by: Maulik Mankad <maulik@ti.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/gadget/composite.c

@@ -813,7 +813,7 @@ composite_setup(struct usb_gadget *gadget, const struct usb_ctrlrequest *ctrl)
 	 */
 	req->zero = 0;
 	req->complete = composite_setup_complete;
-	req->length = USB_BUFSIZ;
+	req->length = 0;
 	gadget->ep0->driver_data = cdev;
 
 	switch (ctrl->bRequest) {