[IA64] SKI Simulator boot

Sorry I didn't notice earlier, but that BUG_ON triggers for me on the
simulator.  AFAICS the mask for itv is set in cpu_init(), which comes
after sal_init().  Consequently on the simulator the itv still has its
start value of zero.  I've probably missed something, but I wonder why
at this stage of the boot you even need to save and restore the itv?

Signed-Off-By: Ian Wienand <ianw@gelato.unsw.edu.au>
Signed-off-by: Tony Luck <tony.luck@intel.com>