cpufreq / Longhaul: Disable driver by default

This is only solution I can think of. User decides if he wants this
driver on his machine. I don't have enough knowledge and time to find
the reason why same code works on some machines and doesn't on others
which use the same, or very similar, chipset and processor.

Signed-off-by: Rafał Bilski <rafalbilski@interia.pl>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>