Use __new__() for case counting

Signed-off-by: Werner Lewis <werner.lewis@arm.com>
diff --git a/scripts/mbedtls_dev/test_generation.py b/scripts/mbedtls_dev/test_generation.py
index aeb551d..f1e085d 100644
--- a/scripts/mbedtls_dev/test_generation.py
+++ b/scripts/mbedtls_dev/test_generation.py
@@ -52,8 +52,9 @@
     test_function = ""
     test_name = ""
 
-    def __init__(self) -> None:
-        type(self).count += 1
+    def __new__(cls, *args, **kwargs):
+        cls.count += 1
+        return super().__new__(cls)
 
     @abstractmethod
     def arguments(self) -> List[str]: