MFC r261577:   Revert r234666.  Clearing TWSI IRQ seems to cause watchdog timeout   on old Yukon II controllers.
MFC r261577:
  Revert r234666.  Clearing TWSI IRQ seems to cause watchdog timeout
  on old Yukon II controllers.

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