This function is useful to fix the endianness of struct
virtio_blk_discard_write_zeroes headers.

Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Message-id: 20190221103314.58500-9-sgarzare@redhat.com
Message-Id: <20190221103314.58500-9-sgarzare@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>