Add comment for OpClass conflict between WavePrefixBitCount and WavePrefixOp.

utils/hct/hctdb.py

@@ -1045,6 +1045,9 @@ class db_dxil(object):
             db_dxil_param(0, "i32", "", "operation result"),
             db_dxil_param(2, "i1", "value", "input value")])
         next_op_idx += 1
+        # WavePrefixBitCount has different signature compare to WavePrefixOp, set its opclass to WavePrefixOp is not correct.
+        # It works now because WavePrefixOp and WavePrefixBitCount don't interfere on overload types.
+        # Keep it unchanged for back-compat.
         self.add_dxil_op("WavePrefixBitCount", next_op_idx, "WavePrefixOp", "returns the count of bits set to 1 on prior lanes", "v", "", [
             db_dxil_param(0, "i32", "", "operation result"),
             db_dxil_param(2, "i1", "value", "input value")])