Bignum test: remove type restrictrion

The special case list type depends on the arity and the subclass. Remove
type restriction to make defining special case lists more flexible and natural.

Signed-off-by: Janos Follath <janos.follath@arm.com>

scripts/mbedtls_dev/bignum_core.py

@@ -243,6 +243,16 @@ class BignumCoreMLA(BignumCoreOperation):
             "\"{:x}\"".format(carry_8)
         ]
 
+    @classmethod
+    def get_value_pairs(cls) -> Iterator[Tuple[str, str]]:
+        """Generator to yield pairs of inputs.
+
+        Combinations are first generated from all input values, and then
+        specific cases provided.
+        """
+        yield from super().get_value_pairs()
+        yield from cls.input_cases
+
     @classmethod
     def generate_function_tests(cls) -> Iterator[test_case.TestCase]:
         """Override for additional scalar input."""