agp: enable optimized agp_alloc_pages methods

The pageattr-array patch that you currently have in tip/master only
enables it for intel-agp, not the others. The attached enables it for
all drivers currently directly using agp_generic_alloc_page() and
agp_generic_destroy_page() (ocal driver is amd-k7-agp).

The new agp_generic_alloc_pages() interface uses the also new
pageattr array interface API. This makes all AGP drivers that
up to now used generic_{alloc,destroy}_page() use it.

Signed-off-by: Rene Herman <rene.herman@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>