Remove hard-coded subdirectory paths for configs

Previously, the subdirectories in which the sub-json files were searched
in were hardcoded. Now, DRAMSys simply searches in the directory of the
base config, making this approach more flexible.

tests/tests_regression/HBM2/hbm2-example.json

@@ -126,11 +126,11 @@
         "tracesetup": [
             {
                 "clkMhz": 1000,
-                "name": "trace1_test4.stl"
+                "name": "traces/trace1_test4.stl"
             },
 	    {
                 "clkMhz": 1000,
-                "name": "trace2_test4.stl"
+                "name": "traces/trace2_test4.stl"
             }
         ]
     }