Fix spurious save prompt when no changes are made

When running menuconfig without an existing .config file, the save
dialog was incorrectly shown even when the user made no changes.

The issue was in _load_config() which returned True when .config was
missing, causing _conf_changed to be initialized to True. This meant
any exit would trigger the save prompt.

Author: jserv

menuconfig.py

@@ -810,13 +810,13 @@ def menuconfig(kconf):
 def _load_config():
     # Loads any existing .config file. See the Kconfig.load_config() docstring.
     #
-    # Returns True if .config is missing or outdated. We always prompt for
-    # saving the configuration in that case.
+    # Returns True if .config exists and is outdated. We prompt for saving the
+    # configuration only if there are actual changes.
 
     print(_kconf.load_config())
     if not os.path.exists(_conf_filename):
-        # No .config
-        return True
+        # No .config - no changes yet
+        return False
 
     return _needs_save()