[AGPGART] Suspend/Resume support for ATI GART

Add suspend/resume support for the ati-agp module

Signed-off-by: Jaco Kroon <jaco@kroon.co.za>
Acked-by: Pavel Machek <pavel@suse.cz>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Dave Jones <davej@redhat.com>