cpufreq: amd-pstate: adjust min/max limit perf

The min/max limit perf values calculated based on frequency
may exceed the reasonable range of perf(highest perf, lowest perf).

Signed-off-by: Meng Li <li.meng@amd.com>
Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>