[PATCH] optional ZONE_DMA: optional ZONE_DMA for ia64

ZONE_DMA less operation for IA64 SGI platform

Disable ZONE_DMA for SGI SN2.  All memory is addressable by all devices and we
do not need any special memory pool.

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Cc: "Luck, Tony" <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>