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>