ACPI / PMIC: Convert to use builtin_platform_driver() macro

All of PMIC OpRegion drivers can't be modules, thus, convert them to use
builtin_platform_driver() macro and remove redundant MODULE_*() macros.

No functional change intended.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/pmic/intel_pmic_bxtwc.c

@@ -412,9 +412,4 @@ static struct platform_driver intel_bxtwc_pmic_opregion_driver = {
 	},
 	.id_table = bxt_wc_opregion_id_table,
 };
-
-static int __init intel_bxtwc_pmic_opregion_driver_init(void)
-{
-	return platform_driver_register(&intel_bxtwc_pmic_opregion_driver);
-}
-device_initcall(intel_bxtwc_pmic_opregion_driver_init);
+builtin_platform_driver(intel_bxtwc_pmic_opregion_driver);