[LITE][OPENCL][Image] use unique_ptr to wrap filter and bias in conv image compute , test=develop

lite/kernels/opencl/scale_image_compute.cc

@@ -42,10 +42,6 @@ class ScaleComputeImage2D : public KernelLite<TARGET(kOpenCL),
                                     build_options_,
                                     time_stamp_);
     VLOG(1) << "kernel_func_name_:" << kernel_func_name_;
-
-    STL::stringstream kernel_key;
-    kernel_key << kernel_func_name_ << build_options_ << time_stamp_;
-    auto kernel = context.cl_context()->GetKernel(kernel_key.str());
   }
 
   void ReInitWhenNeeded() override {