[libata] PM callbacks should be conditionally compiled on CONFIG_PM_SLEEP

This will fix warnings like following when CONFIG_PM_SLEEP is not set:

        warning: 'xxx_suspend' defined but not used [-Wunused-function]
        warning: 'xxx_resume' defined but not used [-Wunused-function]

Because
	SET_SYSTEM_SLEEP_PM_OPS(suspend_fn, resume_fn)

Only references the callbacks on CONFIG_PM_SLEEP (instead of CONFIG_PM).

Cc: Viresh Kumar <viresh.linux@gmail.com>
Cc: linux-ide@vger.kernel.org
Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

drivers/ata/ahci_platform.c

@@ -238,7 +238,7 @@ static int __devexit ahci_remove(struct platform_device *pdev)
 	return 0;
 }
 
-#ifdef CONFIG_PM
+#ifdef CONFIG_PM_SLEEP
 static int ahci_suspend(struct device *dev)
 {
 	struct ahci_platform_data *pdata = dev_get_platdata(dev);

drivers/ata/pata_arasan_cf.c

@@ -914,7 +914,7 @@ static int __devexit arasan_cf_remove(struct platform_device *pdev)
 	return 0;
 }
 
-#ifdef CONFIG_PM
+#ifdef CONFIG_PM_SLEEP
 static int arasan_cf_suspend(struct device *dev)
 {
 	struct ata_host *host = dev_get_drvdata(dev);

drivers/ata/sata_highbank.c

@@ -378,7 +378,7 @@ static int __devexit ahci_highbank_remove(struct platform_device *pdev)
 	return 0;
 }
 
-#ifdef CONFIG_PM
+#ifdef CONFIG_PM_SLEEP
 static int ahci_highbank_suspend(struct device *dev)
 {
 	struct ata_host *host = dev_get_drvdata(dev);