cpufreq / ACPI: Fix not loading acpi-cpufreq driver regression

cpufreq / ACPI: Fix not loading acpi-cpufreq driver regression

Commit d7599cec3a3831e9d48402558 introduced a regression on SMP
systems where the processor core with ACPI id zero is disabled
(typically should be the case because of hyperthreading).
The regression got spread through stable kernels.
On 3.0.X it got introduced via 3.0.18.

Such platforms may be rare, but do exist.
Look out for a disabled processor with acpi_id 0 in dmesg:
ACPI: LAPIC (acpi_id[0x00] lapic_id[0x10] disabled)

This problem has been observed on a:
HP Proliant BL280c G6 blade

This patch restricts the introduced workaround to platforms
with nr_cpu_ids <= 1.

Signed-off-by: Thomas Renninger <trenn@suse.de>
CC: stable@vger.kernel.org
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>