staging/lustre: Update user pointers in struct obd_ioctl_data

Make them void __user * instead of char * (or char __user *),
void * removes the necessity of explicit casts to proper type
where people also need to remember __user qualifiers, so I think
it works better here.

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