[IA64] remove redundant local_irq_save() calls from sn_sal.h

sn_change_memprotect() does a local_irq_save() then calls
ia64_sal_oemcall_nolock() which calls SAL_CALL_NOLOCK()
which also does a local_irq_save().

This patch removes the redundant local_irq_save() and local_irq_restore()
calls in sn_change_memprotect() and sn_inject_error().

Signed-off-by: Russ Anderson <rja@sgi.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>