Small modifications in MemConfig.py and fs.py to support the newly added device for full-system simulation.

Plus a new script called hmctest.py which connects a traffic generator to HMC.
This patch is the last one in the chain of patches aim to model a simple Hybrid Memory Cube device in gem5

Please apply the complete chain before running the simulation.
After applying the patches, you can simply run a full-system simulation:

./build/ARM/gem5.opt configs/example/fs.py \

    --mem-type=HMC_2500_x32 --mem-channels=16 \

    --caches --l2cache \

    --cpu-type=timing
Or a traffic based simulation:

./build/ARM/gem5.opt configs/example/hmctest.py \

    --mem-type=HMC_2500_x32 \

    --mode=RANDOM

gem5 compiles

fs.py executes and Linux boots correctly.

hmctest.py executes correctly, and stats correlate with cycle-accurate simulation