misc: Separate stats file for SystemC-gem5 co-simulation

misc: Separate stats file for SystemC-gem5 co-simulation

In previous versions of systemC-gem5 coupling statistics were not updated
for the systemc-gem5 simulation. systemC-gem5 simulation only need the
previously built config.ini file and normal gem5 simulation has to be run
once to generate config.ini file. Thus stats.txt inside the m5out folder is
redundant for systemC-gem5 simulation. A new stats file is now generated
with the all the statistics for systemC-gem5 simulation. This will also
resolve the stats issue in tlm-sysmtemC simulation.

Committed by Jason Lowe-Power <jason@lowepower.com>