ubi: fastmap: Use kmem_cache_free to deallocate memory

Memory allocated by kmem_cache_alloc() should not be deallocated with
kfree(). Use kmem_cache_free() instead.
Signed-off-by: NPan Bian <bianpan2016@163.com>
Reviewed-by: NBoris Brezillon <boris.brezillon@free-electrons.com>
Signed-off-by: NRichard Weinberger <richard@nod.at>

drivers/mtd/ubi/fastmap.c

@@ -1063,7 +1063,7 @@ int ubi_scan_fastmap(struct ubi_device *ubi, struct ubi_attach_info *ai,
 		e = kmem_cache_alloc(ubi_wl_entry_slab, GFP_KERNEL);
 		if (!e) {
 			while (i--)
-				kfree(fm->e[i]);
+				kmem_cache_free(ubi_wl_entry_slab, fm->e[i]);
 
 			ret = -ENOMEM;
 			goto free_hdr;