cpufreq: Prefer to print cpuid in MIN/MAX QoS register error message

When a cpufreq_policy is allocated, the cpus, related_cpus and real_cpus
of policy are still unset. Therefore, it is preferable to print the
passed 'cpu' parameter instead of a empty 'cpus' cpumask in error
message when registering MIN/MAX QoS notifier fails.

Signed-off-by: Liao Chang <liaochang1@huawei.com>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>