dynamicoverlay: Fix memory leak

In spu/dynamicoverlay/dynamicoverlay_commands.c in exec_DataSharedMem(), memory is allocated via the call to picture_New(). This memory is correctly freed via picture_Release() if an error occurs, but if no error occurs and the function proceeds normally, the memory is never freed.

When the DataSharedMem routine is called repeatedly (e.g., to update a picture continuously), this leak accumulates very quickly.