x86, ioapic: Restore ioapic entries during resume properly

In mask/restore_ioapic_entries() we should be restoring ioapic
entries when ioapics[apic].saved_registers is not NULL.

Fix the typo and address the resume hang regression reported by
Linus.

This was not found sooner because the systems where these
changes were tested on kept the IO-APIC entries intact over
resume.

Reported-and-tested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Daniel J Blueman <daniel.blueman@gmail.com>
Link: http://lkml.kernel.org/r/1306259131.7171.7.camel@sbsiddha-MOBL3.sc.intel.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>