SDS: Install better fix for 2x real-time clock speed problem

Received better fix from Mark Pizzolato for the problem of having 120 clock interrupts per second instead of 60. Tested for several hours and verified that wall-clock time matches TSS monitor time.
SDS: Update README.md for 940 enhancements
SCP: Removed the irrelevant sim_deb_PC variable since it duplicates the role sim_PC simulator variable.