airo: correct proc entry creation interfaces

* use proc_mkdir_mode() instead of create_proc_entry(S_IFDIR|...),
  export proc_mkdir_mode() for that, oh well.
* don't supply S_IFREG to proc_create_data(), it's unnecessary

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>