cpufreq: amd-pstate: Fix min_perf assignment in amd_pstate_adjust_perf()

In the function amd_pstate_adjust_perf(), the 'min_perf' variable is set
to 'highest_perf' instead of 'lowest_perf'.

Fixes: 1d215f03 ("cpufreq: amd-pstate: Add fast switch function for AMD P-State")
Reported-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Reviewed-by: Perry Yuan <Perry.Yuan@amd.com>
Signed-off-by: Tor Vic <torvic9@mailbox.org>
Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>
Cc: 6.1+ <stable@vger.kernel.org> # 6.1+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>