efl_ui_layout: add EFL_OBJECT_OP_FUNC for callback_priority_add
This code is missing after migration.
See also, commit
c471f4a90966e03d1cc80f204f3c7c20ef869618.
Fixes complier warnings.
```
[ 190s] [1723/2497] Compiling C object 'src/lib/elementary/f70ca57@@elementary@sha/efl_ui_layout.c.o'.
[ 190s] ../src/lib/elementary/efl_ui_layout.c:3272:1: warning: '_efl_ui_layout_base_efl_object_event_callback_array_priority_add' defined but not used [-Wunused-function]
[ 190s] 3272 | _efl_ui_layout_base_efl_object_event_callback_array_priority_add(Eo *obj, Efl_Ui_Layout_Data *pd, const Efl_Callback_Array_Item *array, Efl_Callback_Priority priority, const void *user_data)
[ 190s] ../src/lib/elementary/efl_ui_layout.c:3261:1: warning: '_efl_ui_layout_base_efl_object_event_callback_priority_add' defined but not used [-Wunused-function]
[ 190s] 3261 | _efl_ui_layout_base_efl_object_event_callback_priority_add(Eo *obj, Efl_Ui_Layout_Data *pd, const Efl_Event_Description *desc, Efl_Callback_Priority priority, Efl_Event_Cb func, const void *user_data)
```
@tizen_fix
Change-Id: I8b212b6e36ba151a593291091bd119794f035c93