acpi-cpufreq: skip loading acpi_cpufreq after intel_pstate

If the hw supports intel_pstate and acpi_cpufreq, intel_pstate will
get loaded first.

acpi_cpufreq_init() will call acpi_cpufreq_early_init()
and that will allocate perf data and init those perf data in ACPI core,
(that will cover all CPUs). But later it will free them as
cpufreq_register_driver(acpi_cpufreq) will fail as intel_pstate is
already registered

Use cpufreq_get_current_driver() to check if we can skip the
acpi_cpufreq loading.
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/cpufreq/acpi-cpufreq.c

@@ -986,6 +986,10 @@ static int __init acpi_cpufreq_init(void)
 {
 	int ret;
 
+	/* don't keep reloading if cpufreq_driver exists */
+	if (cpufreq_get_current_driver())
+		return 0;
+
 	if (acpi_disabled)
 		return 0;