[libata] fix smatch warning for zpodd_wake_dev

Fix a smatch warning caused by an useless pointer check.
The context parameter (aka. ata_dev) will never be NULL until we remove
the acpi notification handler, so it is pointless to check it for NULL.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Aaron Lu <aaron.lu@intel.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

drivers/ata/libata-zpodd.c

@@ -246,8 +246,7 @@ static void zpodd_wake_dev(acpi_handle handle, u32 event, void *context)
 	struct zpodd *zpodd = ata_dev->zpodd;
 	struct device *dev = &ata_dev->sdev->sdev_gendev;
 
-	if (event == ACPI_NOTIFY_DEVICE_WAKE && ata_dev &&
-			pm_runtime_suspended(dev)) {
+	if (event == ACPI_NOTIFY_DEVICE_WAKE && pm_runtime_suspended(dev)) {
 		zpodd->from_notify = true;
 		pm_runtime_resume(dev);
 	}