Fix a typo; left out preprocessor conditional for sigoff variable, which is only used by TCP_SIGNATURE code.
Fix a typo; left out preprocessor conditional for sigoff variable, which
is only used by TCP_SIGNATURE code.

Noticed by:	Roop Nanuwa

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase