AMD systems that support preferred cores will use "166" as their numerator for max frequency calculations instead of "255". Add a function for detecting preferred cores by looking at the highest perf value on all cores. If preferred cores are enabled return 166 and if disabled the value in the highest perf register. As the function will be called multiple times, cache the values for the boost numerator and if preferred cores will be enabled in global variables. Reviewed-by: Gautham R. Shenoy <gautham.shenoy@amd.com> Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>