cpufreq / intel_pstate: Do not load on VM that does not report max P state.

It seems some VMs support the P state MSRs but return zeros. Fail
gracefully if we are running in this environment.

References: https://bugzilla.redhat.com/show_bug.cgi?id=916833Reported-by: NJosh Boyer <jwboyer@redhat.com>
Signed-off-by: NDirk Brandewie <dirk.j.brandewie@intel.com>
Acked-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/cpufreq/intel_pstate.c

@@ -662,6 +662,9 @@ static int intel_pstate_set_policy(struct cpufreq_policy *policy)
 
 	cpu = all_cpu_data[policy->cpu];
 
+	if (!policy->cpuinfo.max_freq)
+		return -ENODEV;
+
 	intel_pstate_get_min_max(cpu, &min, &max);
 
 	limits.min_perf_pct = (policy->min * 100) / policy->cpuinfo.max_freq;