Fix compilationw with amgcl/vexcl and without CUDA/OpenCL.

There is no reason to omit WellContributions if neither CUDA nor
OpenCL is found as the implementations/functions only use C++-
To the contrary, the defines used for deactivating were not
consistent with usage elsewhere and resulted in compiler erorrs
for exotic configuration

opm/simulators/wells/MultisegmentWellEval.hpp

@@ -54,10 +54,8 @@ template<typename FluidSystem, typename Indices, typename Scalar>
 class MultisegmentWellEval : public MultisegmentWellGeneric<Scalar>
 {
 public:
-#if HAVE_CUDA || HAVE_OPENCL
         /// add the contribution (C, D, B matrices) of this Well to the WellContributions object
         void addWellContribution(WellContributions& wellContribs) const;
-#endif
 
 protected:
     // TODO: for now, not considering the polymer, solvent and so on to simplify the development process.