cpufreq: intel_pstate: Delete intel_pstate sysfs if failed to register the driver

There is a corner case that if the intel_pstate driver fails to be
registered (might be due to invalid MSR access) and acpi_cpufreq
takse over, the intel_pstate sysfs interface is still populated
which may confuse user space (turbostat for example):

grep . /sys/devices/system/cpu/cpu0/cpufreq/scaling_driver
acpi-cpufreq

grep . /sys/devices/system/cpu/intel_pstate/*
/sys/devices/system/cpu/intel_pstate/max_perf_pct:0
/sys/devices/system/cpu/intel_pstate/min_perf_pct:0
grep: /sys/devices/system/cpu/intel_pstate/no_turbo: Resource temporarily unavailable
grep: /sys/devices/system/cpu/intel_pstate/num_pstates: Resource temporarily unavailable
/sys/devices/system/cpu/intel_pstate/status:off
grep: /sys/devices/system/cpu/intel_pstate/turbo_pct: Resource temporarily unavailable

The mere presence of the intel_pstate sysfs interface does not mean
that intel_pstate is in use (for example, echo "off" to "status"),
but it should not be created in the failing case.

Fix this issue by deleting the intel_pstate sysfs if the driver
registration fails.
Reported-by: Wendy Wang <wendy.wang@intel.com>
Suggested-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Acked-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com
[ rjw: Refactor code to avoid jumps, change function name, changelog edits ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/cpufreq/intel_pstate.c

@@ -1420,6 +1420,24 @@ static void __init intel_pstate_sysfs_expose_params(void)
 	}
 }
 
+static void __init intel_pstate_sysfs_remove(void)
+{
+	if (!intel_pstate_kobject)
+		return;
+
+	sysfs_remove_group(intel_pstate_kobject, &intel_pstate_attr_group);
+
+	if (!per_cpu_limits) {
+		sysfs_remove_file(intel_pstate_kobject, &max_perf_pct.attr);
+		sysfs_remove_file(intel_pstate_kobject, &min_perf_pct.attr);
+
+		if (x86_match_cpu(intel_pstate_cpu_ee_disable_ids))
+			sysfs_remove_file(intel_pstate_kobject, &energy_efficiency.attr);
+	}
+
+	kobject_put(intel_pstate_kobject);
+}
+
 static void intel_pstate_sysfs_expose_hwp_dynamic_boost(void)
 {
 	int rc;
@@ -3063,8 +3081,10 @@ static int __init intel_pstate_init(void)
 	mutex_lock(&intel_pstate_driver_lock);
 	rc = intel_pstate_register_driver(default_driver);
 	mutex_unlock(&intel_pstate_driver_lock);
-	if (rc)
+	if (rc) {
+		intel_pstate_sysfs_remove();
 		return rc;
+	}
 
 	if (hwp_active) {
 		const struct x86_cpu_id *id;