[Serialization] Exit right way on any invalid swiftmodule file

The previous behavior kept going even after we reported an invalid
swiftmodule. As such it ended up losing the precise invalid reason and
returned Malformed later on.

Author: xymus

lib/Serialization/ModuleFileSharedCore.cpp

@@ -544,7 +544,7 @@ ValidationInfo serialization::validateSerializedAST(
           requiresOSSAModules, requiresRevisionMatch,
           requiredSDK,
           extendedInfo, localObfuscator);
-      if (result.status == Status::Malformed)
+      if (result.status != Status::Valid)
         return result;
     } else if ((dependencies || searchPaths) &&
                result.status == Status::Valid &&