[CPUFREQ] Longhaul - Check ACPI "BM DMA in progress" bit

It is good idea to wait for PCI bus to become idle before
frequency change. Thanks to ACPI it is possible. It makes
sense only when northbridge support is in use because it is
only case in which we can disable arbiter after check if PCI
bus is busy.

Signed-off-by: Rafal Bilski <rafalbilski@interia.pl>
Signed-off-by: Dave Jones <davej@redhat.com>