Use raw_smp_processor_id() instead of plain smp_processor_id() in
do_service_request(), otherwise we may get some errors with the driver
enabled:

 BUG: using smp_processor_id() in preemptible [00000000] code: (udev-worker)/208
 caller is loongson3_cpufreq_probe+0x5c/0x250 [loongson3_cpufreq]
Reported-by: Xi Ruoyao <xry111@xry111.site>
Tested-by: Binbin Zhou <zhoubinbin@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>