[IA64] XPC heartbeat timer function must run on CPU 0

Currently, XPC's heartbeat timer function runs on whatever CPU modprobe/insmod
ran on when XPC was started. To avoid the heartbeat from being delayed for
long periods the timer function must run on CPU 0.

N.B. Altix doesn't currently allow cpu0 to be taken offline, so this is
safe for now.  This code must be revised when offline of cpu0 is enabled.

Signed-off-by: Dean Nelson <dcn@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>