[PATCH] correct slow acpi_pm rating

On Bob's machine clocksource is selecting PIT over the ACPI PM timer,
because he has the PIIX4 bug.  That bug drops the ACPI PM timers rating
to the same as the PIT, so that's why you're getting the PIT.

Realistically, the PIT is much slower then even the triple read ACPI PM,
so the de-ranking code is probably dropping it too far.

So don't drop ACPI PM quite so low if we see the PIIX4 bug.

Signed-off-by: John Stultz <johnstul@us.ibm.com>
Cc: Bob Tracy <rct@gherkin.frus.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Andi Kleen <ak@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>