Restoring AIO is quite simple. Once all VMAs are put in
their places we can call io_setup() to let kernel create
the context back and then move the ring into proper place.

Another thing we should "restore" is the context ID. But
the thing is, upon ring creation kernel repots the ring
start address as this ID. And there's a patch in the -next
tree that changes the ID when we remap the ring. That
said after AIO context creation and ring remap we need
to check that the new ID is seen by the kernel.
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>