[dv/tool] Add support to choose sub-cfgs

Add a parse_arg for user to choose which dut to run in a master cfg that
contains more than one sub-cfgs.

Signed-off-by: Cindy Chen <chencindy@google.com>
diff --git a/util/dvsim/SimCfg.py b/util/dvsim/SimCfg.py
index 55157c2..e16a519 100644
--- a/util/dvsim/SimCfg.py
+++ b/util/dvsim/SimCfg.py
@@ -127,9 +127,11 @@
         # Set the title for simulation results.
         self.results_title = self.name.upper() + " Simulation Results"
 
-        # Stuff below only pertains to individual cfg (not master cfg).
-        if not self.is_master_cfg:
-            # Print info
+        # Stuff below only pertains to individual cfg (not master cfg)
+        # or individual selected cfgs (if select_cfgs is configured via command line)
+        # TODO: find a better way to support select_cfgs
+        if not self.is_master_cfg and (not self.select_cfgs or self.name in self.select_cfgs):
+            # Print info:
             log.info("[scratch_dir]: [%s]: [%s]", self.name, self.scratch_path)
 
             # Set directories with links for ease of debug / triage.