staging: rtl8188eu: Remove usb_vendor_req.h header file

driver doesn't need usb_vendor_req.h.

Signed-off-by: navin patidar <navin.patidar@gmail.com>
Reviewed-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>