amd-pstate: Update cppc_req_cached in fast_switch case

The function msr_update_perf() does not cache the new value that is
written to MSR_AMD_CPPC_REQ into the variable cpudata->cppc_req_cached
when the update is happening from the fast path.

Fix that by caching the value everytime the MSR_AMD_CPPC_REQ gets
updated.

This issue was discovered by Claude Opus 4.6 with the aid of Chris
Mason's AI review-prompts
(https://github.com/masoncl/review-prompts/tree/main/kernel).

Assisted-by: Claude:claude-opus-4.6 review-prompts/linux
Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org>
Fixes: fff3957 ("cpufreq/amd-pstate: Always write EPP value when updating perf")
Signed-off-by: Gautham R. Shenoy <gautham.shenoy@amd.com>
Signed-off-by: Mario Limonciello (AMD) <superm1@kernel.org>

Author: gautshen

drivers/cpufreq/amd-pstate.c

@@ -261,7 +261,6 @@ static int msr_update_perf(struct cpufreq_policy *policy, u8 min_perf,
 
 	if (fast_switch) {
 		wrmsrq(MSR_AMD_CPPC_REQ, value);
-		return 0;
 	} else {
 		int ret = wrmsrq_on_cpu(cpudata->cpu, MSR_AMD_CPPC_REQ, value);