cpufreq/amd-pstate: Fix the return value of amd_pstate_fast_switch()

cpufreq_driver->fast_switch() callback expects a frequency as a return
value. amd_pstate_fast_switch() was returning the return value of
amd_pstate_update_freq(), which only indicates a success or failure.

Fix this by making amd_pstate_fast_switch() return the target_freq
when the call to amd_pstate_update_freq() is successful, and return
the current frequency from policy->cur when the call to
amd_pstate_update_freq() is unsuccessful.

Fixes: 4badf2eb ("cpufreq: amd-pstate: Add ->fast_switch() callback")
Acked-by: Huang Rui <ray.huang@amd.com>
Reviewed-by: Wyes Karny <wyes.karny@amd.com>
Reviewed-by: Perry Yuan <perry.yuan@amd.com>
Cc: 6.4+ <stable@vger.kernel.org> # v6.4+
Signed-off-by: Gautham R. Shenoy <gautham.shenoy@amd.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/cpufreq/amd-pstate.c

@@ -518,7 +518,9 @@ static int amd_pstate_target(struct cpufreq_policy *policy,
 static unsigned int amd_pstate_fast_switch(struct cpufreq_policy *policy,
 				  unsigned int target_freq)
 {
-	return amd_pstate_update_freq(policy, target_freq, true);
+	if (!amd_pstate_update_freq(policy, target_freq, true))
+		return target_freq;
+	return policy->cur;
 }
 
 static void amd_pstate_adjust_perf(unsigned int cpu,