To allow an alternative kernel profiler using the ia64
perfomance counters to be loaded as a module, a couple
of small changes are needed.

1) Define a new 'irqflags' bit (SA_PERCPU_IRQ) to allow a module
to request a per-cpu irq.

2) Export init_tasks[] so that the module can adjust the state
of psr.pp in the idle tasks for all CPUs.

I've attached the patch rather than inlining it in the hope that
outlook won't sabotage it by folding long lines or playing with
tabs and spaces.

-Tony Luck