Fix icc compiler warning

ndb/src/kernel/blocks/dbtux/Dbtux.hpp:
  Removed second forward declaration of "struct DescEnt"

ndb/src/kernel/blocks/dbtux/Dbtux.hpp

@@ -342,7 +342,6 @@ private:
    * Complete metadata for one index. The array of attributes has
    * variable size.
    */
-  struct DescEnt;
   friend struct DescEnt;
   struct DescEnt {
     DescHead m_descHead;