x86 PM: update stale comments

In some suspend and hibernation files in arch/x86/power there are
comments referring to arch/x86-64 and arch/i386 .  Update them to
reflect the current code layout.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>