ACPI / PM: Fix unused function warnings for CONFIG_PM_SLEEP

According to compiler warnings, several suspend/resume functions
in ACPI drivers are not used for CONFIG_PM_SLEEP unset, so add
#ifdefs to prevent them from being built in that case.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
diff --git a/drivers/acpi/fan.c b/drivers/acpi/fan.c
index 669d9ee..bc36a47 100644
--- a/drivers/acpi/fan.c
+++ b/drivers/acpi/fan.c
@@ -53,8 +53,10 @@
 };
 MODULE_DEVICE_TABLE(acpi, fan_device_ids);
 
+#ifdef CONFIG_PM_SLEEP
 static int acpi_fan_suspend(struct device *dev);
 static int acpi_fan_resume(struct device *dev);
+#endif
 static SIMPLE_DEV_PM_OPS(acpi_fan_pm, acpi_fan_suspend, acpi_fan_resume);
 
 static struct acpi_driver acpi_fan_driver = {
@@ -184,6 +186,7 @@
 	return 0;
 }
 
+#ifdef CONFIG_PM_SLEEP
 static int acpi_fan_suspend(struct device *dev)
 {
 	if (!dev)
@@ -207,6 +210,7 @@
 
 	return result;
 }
+#endif
 
 static int __init acpi_fan_init(void)
 {