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

objects/MemTest.mpy

@@ -3,10 +3,7 @@ simobj MemTest(SimObject):
     cache = Param.BaseCache("L1 cache")
     check_mem = Param.FunctionalMemory("check memory")
     main_mem = Param.FunctionalMemory("hierarchical memory")
-    max_loads_all_threads = Param.Counter(0,
-        "terminate when all threads have reached this load count")
-    max_loads_any_thread = Param.Counter(0,
-        "terminate when any thread reaches this load count")
+    max_loads = Param.Counter("number of loads to execute")
     memory_size = Param.Int(65536, "memory size")
     percent_copies = Param.Percent(0, "target copy percentage")
     percent_dest_unaligned = Param.Percent(50,