Clean up CPU stuff and make it use params structs

Clean up CPU stuff and make it use params structs

cpu/base_cpu.cc:
cpu/base_cpu.hh:
    Convert the CPU stuff to use a params struct
cpu/memtest/memtest.cc:
    The memory tester is really not a cpu, so don't derive from
    BaseCPU since it just makes things a pain in the butt.  Keep
    track of max loads in the memtest class now that the base class
    doesn't do it for us.
    Don't have any default parameters.
cpu/memtest/memtest.hh:
    The memory tester is really not a cpu, so don't derive from
    BaseCPU since it just makes things a pain in the butt.  Keep
    track of max loads in the memtest class now that the base class
    doesn't do it for us.
cpu/simple_cpu/simple_cpu.cc:
    Convert to use a params struct.
    remove default parameters
cpu/simple_cpu/simple_cpu.hh:
    convert to use a params struct
cpu/trace/opt_cpu.cc:
cpu/trace/opt_cpu.hh:
cpu/trace/trace_cpu.cc:
cpu/trace/trace_cpu.hh:
    this isn't really a cpu.  don't derive from BaseCPU
objects/MemTest.mpy:
    we only need one max_loads parameter
sim/main.cc:
    Don't check for the number of CPUs since we may be doing something
    else going on.  If we don't have anything to simulate, the
    simulator will exit anyway.

--HG--
extra : convert_revision : 2195a34a9ec90b5414324054ceb3bab643540dd5