mm: zram: fix build error when zram wb disabled

fix build error 
when zram wb disabled

Change-Id: I59b1dc0756d10424b76df587d8f9a3f923647882
Signed-off-by: lulei1 <lulei1@motorola.com>
Reviewed-on: https://gerrit.mot.com/2157751
SLTApproved: Slta Waiver
SME-Granted: SME Approvals Granted
Tested-by: Jira Key
Reviewed-by: Zhangqing Huang <huangzq2@motorola.com>
Reviewed-by: Wang Wang <wangwang1@lenovo.com>
Submit-Approved: Jira Key

drivers/block/zram/zram_drv.c

@@ -1755,6 +1755,7 @@ static void zram_slot_free_notify(struct block_device *bdev,
 /* Moto lulei1: check sync_io state on swap entry,
  * return 0 on wb page, else return 1.
  */
+#ifdef CONFIG_ZRAM_WRITEBACK
 static int zram_ioctl(struct block_device *bdev, fmode_t mode,
 				 unsigned int cmd, unsigned long index)
 {
@@ -1763,16 +1764,14 @@ static int zram_ioctl(struct block_device *bdev, fmode_t mode,
 
 	if (cmd != SWP_SYNCHRONOUS_IO) return -EINVAL;
 
-#ifdef CONFIG_ZRAM_WRITEBACK
 	zram = bdev->bd_disk->private_data;
 	zram_slot_lock(zram, index);
 	has_sync_io = zram_test_flag(zram, index, ZRAM_WB) ? 0 : 1;
 	zram_slot_unlock(zram, index);
-#endif
 
 	return has_sync_io;
 }
-
+#endif
 
 static int zram_rw_page(struct block_device *bdev, sector_t sector,
 		       struct page *page, unsigned int op)
@@ -1966,7 +1965,9 @@ static int zram_open(struct block_device *bdev, fmode_t mode)
 static const struct block_device_operations zram_devops = {
 	.open = zram_open,
 	.swap_slot_free_notify = zram_slot_free_notify,
+#ifdef CONFIG_ZRAM_WRITEBACK
 	.ioctl = zram_ioctl,
+#endif
 	.rw_page = zram_rw_page,
 	.owner = THIS_MODULE
 };