Use gst_element_class_set_details_simple() instead. If you want to
convert automatically, here's a script:

for file in `git grep -l GstElementDetails`; do
  sed -i -n -r '
    1h
    1!H
    $ {
      g
      s/((\/\*[^\n]*\*\/)?\n)*[^\n]*GstElementDetails .* =\s*GST_ELEMENT_DETAILS\s*\((\"[^\"]*\",\s*\"[^\"]*\",\s*\"[^\"]*\",\s*(\"[^\"]*\"\s*)*)\);\n*(.*)gst_element_class_set_details \(([^,]*),\s*[^)]*\)/\n\n\5gst_element_class_set_details_simple (\6, \3)/
      s/((\/\*[^\n]*\*\/)?\n)*[^\n]*GstElementDetails .* =\s*\{\s*(\"[^\"]*\",\s*\"[^\"]*\",\s*\"[^\"]*\",\s*(\"[^\"]*\"\s*)*)\};\n*(.*)gst_element_class_set_details \(([^,]*),\s*[^)]*\)/\n\n\5gst_element_class_set_details_simple (\6, \3)/
      p
    }' $file
  ~/gst/gstreamer/tools/gst-indent $file
done