[IA64-SGI] disable msi for all altix pci devices

Temporary patch to make pci_enable_msi() fail gracefully on altix.  Will be
removed after 2.6.16 releases and the msi abstraction patches start flowing.

Signed-off-by: Mark Maule <maule@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>