cpufreq/amd-pstate: Add missing NULL ptr check in amd_pstate_update

commit 426db24 upstream.

Check if policy is NULL before dereferencing it in amd_pstate_update.

Fixes: e8f555d ("cpufreq/amd-pstate: fix setting policy current frequency value")
Signed-off-by: Dhananjay Ugwekar <dhananjay.ugwekar@amd.com>
Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>
Reviewed-by: Gautham R. Shenoy <gautham.shenoy@amd.com>
Link: https://lore.kernel.org/r/20250205112523.201101-11-dhananjay.ugwekar@amd.com
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
[Minor context change fixed.]
Signed-off-by: Wenshan Lan <jetlan9@163.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: dhananjay-AMD

drivers/cpufreq/amd-pstate.c

@@ -482,6 +482,9 @@ static void amd_pstate_update(struct amd_cpudata *cpudata, u32 min_perf,
 	u32 nominal_perf = READ_ONCE(cpudata->nominal_perf);
 	u64 value = prev;
 
+	if (!policy)
+		return;
+
 	min_perf = clamp_t(unsigned long, min_perf, cpudata->min_limit_perf,
 			cpudata->max_limit_perf);
 	max_perf = clamp_t(unsigned long, max_perf, cpudata->min_limit_perf,