cpufreq: amd-pstate: change amd-pstate driver to be built-in type

Currently when the amd-pstate and acpi_cpufreq are both built into
kernel as module driver, amd-pstate will not be loaded by default
in this case.

Change amd-pstate driver as built-in type, it will resolve the loading
sequence problem to allow user to make amd-pstate driver as the default
cpufreq scaling driver.
Acked-by: Huang Rui <ray.huang@amd.com>
Reviewed-by: Gautham R. Shenoy <gautham.shenoy@amd.com>
Tested-by: Wyes Karny <wyes.karny@amd.com>
Signed-off-by: Perry Yuan <Perry.Yuan@amd.com>
Fixes: ec437d71 ("cpufreq: amd-pstate: Introduce a new AMD P-State driver to support future processors")
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/cpufreq/Kconfig.x86

@@ -35,7 +35,7 @@ config X86_PCC_CPUFREQ
 	  If in doubt, say N.
 
 config X86_AMD_PSTATE
-	tristate "AMD Processor P-State driver"
+	bool "AMD Processor P-State driver"
 	depends on X86 && ACPI
 	select ACPI_PROCESSOR
 	select ACPI_CPPC_LIB if X86_64

drivers/cpufreq/amd-pstate.c

@@ -663,16 +663,7 @@ static int __init amd_pstate_init(void)
 
 	return ret;
 }
-
-static void __exit amd_pstate_exit(void)
-{
-	cpufreq_unregister_driver(&amd_pstate_driver);
-
-	amd_pstate_enable(false);
-}
-
-module_init(amd_pstate_init);
-module_exit(amd_pstate_exit);
+device_initcall(amd_pstate_init);
 
 MODULE_AUTHOR("Huang Rui <ray.huang@amd.com>");
 MODULE_DESCRIPTION("AMD Processor P-state Frequency Driver");