fs/aio.c: make 3 functions static

Make the following needlessly global functions static:

- __put_ioctx()
- lookup_ioctx()
- io_submit_one()

Signed-off-by: Adrian Bunk <bunk@kernel.org>
Cc: Zach Brown <zach.brown@oracle.com>
Cc: Benjamin LaHaise <bcrl@kvack.org>
Cc: Badari Pulavarty <pbadari@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>