aacraid: fix security hole (CVE-2007-4308)

On the SCSI layer ioctl path there is no implicit permissions check for
ioctls (and indeed other drivers implement unprivileged ioctls). aacraid
however allows all sorts of very admin only things to be done so should
check.

Signed-off-by: Alan Cox <alan@redhat.com>
Acked-by: Mark Salyzyn <mark_salyzyn@adaptec.com>
Signed-off-by: Adrian Bunk <bunk@kernel.org>