[CPUFREQ] fix cpuinfo_cur_freq for CPU_HW_PSTATE

This fixes the cpuinfo_cur_freq value by using the correct
find_khz_freq_from_fiddid() when the CPU uses hardware p-states.

Signed-off-by: Joachim Deguara <joachim.deguara@amd.com>
Acked-by: Mark Langsdorf <mark.langsdorf@amd.com>
Signed-off-by: Dave Jones <davej@redhat.com>