Remove unneeded, undesirable cast of void*.

Cc: Jeff Garzik <jeff@garzik.org>
Cc: Sonic Zhang <sonic.adi@gmail.com>
Cc: Tejun Heo <htejun@gmail.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NJeff Garzik <jeff@garzik.org>