configs,ext: gem5 SST bridge calls m5.instantiate() in gem5

This change updates the gem5 SST bridge to call m5.instantiate()
in the gem5 config script instead of in the SST component. This
allows more flexibility for the gem5-SST setup, as we can now write
traffic generators using the bridge.

Change-Id: I510a8c15f8fb00bdbdd60dafa2d9f5ad011e48f2
Signed-off-by: Kaustav Goswami <kggoswami@ucdavis.edu>

ext/sst/gem5.cc

@@ -204,13 +204,7 @@ gem5Component::init(unsigned phase)
 
     if (phase == 0) {
         initPython(args.size(), &args[0]);
-
-        const std::vector<std::string> m5_instantiate_commands = {
-            "import m5",
-            "m5.instantiate()"
-        };
-        execPythonCommands(m5_instantiate_commands);
-
+        // m5.instantiate() was moved to the gem5 script.
         // calling SimObject.startup()
         const std::vector<std::string> simobject_setup_commands = {
             "import atexit",