sata/mvebu: use #ifdef around suspend/resume code

The newly added suspend/resume implementation for ahci_mvebu causes
a link error when CONFIG_PM_SLEEP is disabled:

ERROR: "ahci_platform_suspend_host" [drivers/ata/ahci_mvebu.ko] undefined!
ERROR: "ahci_platform_resume_host" [drivers/ata/ahci_mvebu.ko] undefined!

This adds the same #ifdef here that exists in the ahci_platform driver
which defines the above functions.

Signed-off-by: Arnd Bergmann <[e-mail]>
Fixes: d6ecf1581488 ("ata: ahci_mvebu: add suspend/resume support")
Acked-by: Thomas Petazzoni <[e-mail]>
Signed-off-by: Tejun Heo <[e-mail]>

drivers/ata/ahci_mvebu.c

···
 	writel(0x80, hpriv->mmio + AHCI_VENDOR_SPECIFIC_0_DATA);
 }
 
+#ifdef CONFIG_PM_SLEEP
 static int ahci_mvebu_suspend(struct platform_device *pdev, pm_message_t state)
 {
 	return ahci_platform_suspend_host(&pdev->dev);
···
 
 	return ahci_platform_resume_host(&pdev->dev);
 }
+#else
+#define ahci_mvebu_suspend NULL
+#define ahci_mvebu_resume NULL
+#endif
 
 static const struct ata_port_info ahci_mvebu_port_info = {
 	.flags	   = AHCI_FLAG_COMMON,