staging/lustre/llite: Move ll_dirent_type_get and make it static

ll_dirent_type_get is only used in one place in llite/dir.c,
so move it there.

Signed-off-by: Oleg Drokin <green@linuxhacker.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>