Use out_prefix instead of "w" in spm.Normalize12

Currently, for the Normalize12 process in spm, the user can define the out_prefix parameter, but this is not used to generate output, as it is hard-coded to 'w' in Normalize12._list_outputs().

Author: servoz

Diff for: nipype/interfaces/spm/preprocess.py

@@ -1491,13 +1491,13 @@ def _list_outputs(self):
                 filelist = ensure_list(self.inputs.apply_to_files)
                 for f in filelist:
                     if isinstance(f, list):
-                        run = [fname_presuffix(in_f, prefix="w") for in_f in f]
+                        run = [fname_presuffix(in_f, prefix=self.inputs.out_prefix) for in_f in f]
                     else:
-                        run = [fname_presuffix(f, prefix="w")]
+                        run = [fname_presuffix(f, prefix=self.inputs.out_prefix)]
                     outputs["normalized_files"].extend(run)
             if isdefined(self.inputs.image_to_align):
                 outputs["normalized_image"] = fname_presuffix(
-                    self.inputs.image_to_align, prefix="w"
+                    self.inputs.image_to_align, prefix=self.inputs.out_prefix
                 )
 
         return outputs