[PERFORMANCE] removed unused variables from TransferDescription class

Should save a few byte for every transmitted data via bytestream.

Change-Id: I3b4abb5fcc052991d7fbbcbf1d1507bc6ba06ea2
Reviewed-on: http://saros-build.imp.fu-berlin.de/gerrit/919
Tested-by: Jenkins CI
Reviewed-by: Holger Freyther <holger@freyther.de>
Reviewed-by: Stefan Rossbach <srossbach@arcor.de>