ACPI: don't check power state after _ON/_OFF

We used to evaluate _STA to check the power state of a device after
running _ON or _OFF.  But as far as I can tell, there's no benefit
to evaluating _STA, and sometimes we trip over bugs when BIOSes don't
implement _STA correctly.

Yakui says Windows XP doesn't evaluate _STA during power transition.
So let's skip it in Linux, too.  It's conceivable that we'll need to
check _STA in the future for some reason, but until we do, I don't
see a reason to clutter this code path.

References:
    http://bugzilla.kernel.org/show_bug.cgi?id=13243
    http://marc.info/?l=linux-acpi&m=124166053803753&w=2
    http://marc.info/?l=linux-acpi&m=124175761408256&w=2
    http://marc.info/?l=linux-acpi&m=124210593114061&w=2

Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Acked-by: Matthew Garrett <mjg59@srcf.ucam.org>
Signed-off-by: Len Brown <len.brown@intel.com>