[Refactor] use get_accumulator_dt_cands as part of DataType rf.

src/finn/custom_op/fpgadataflow/channelwise_op_batch.py

@@ -56,7 +56,7 @@ def get_smallest_possible(vals):
     for v in vals:
         assert int(v) == v, "Error float value"
 
-    for k in DataType.__members__:
+    for k in DataType.get_accumulator_dt_cands():
         dt = DataType[k]
 
         if dt in [DataType["BIPOLAR"], DataType["TERNARY"], DataType["FLOAT32"]]:

src/finn/transformation/fpgadataflow/convert_to_hls_layers.py

@@ -1251,7 +1251,7 @@ class InferChannelwiseLinearLayer(Transformation):
         for v in vals:
             assert int(v) == v, "Error float value"
 
-        for k in DataType.__members__:
+        for k in DataType.get_accumulator_dt_cands():
             dt = DataType[k]
 
             if dt in [DataType["BIPOLAR"], DataType["TERNARY"], DataType["FLOAT32"]]: