MSTP update - 20: correcting reference for CIST port extended parameters

Added corrections for referencing #CIST #port #extended #parameter s #through the #parent #STP #port in MSTP module. The hard-linked CIST port extended configuration entries enables accessing them directly from the standard STP port entries.

#802-1S #MSTP update 20 ...
[commit 5a61ffb0c9a66e50b2a822ca557614bd9650d01a]