[IA64] - Altix: hotplug after intr redirect can crash system

When redirecting a device interrupt on SN, not all links
between platform specific structures are being updated.
This can result in a system crash if an interrupt
redirection is followed by an unplug of that device.

The complete fix also requires a prom update. Though,
this patch is backward compatable and not dependent on
the prom patch.

Signed-off-by: John Keller <jpk@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>