UBI: fix freeing ubi->vtbl while unloading

ubi->vtbl is allocated using vmalloc() in vtbl.c empty_create_lvol(),
but it is freed in build.c with kfree()

Signed-off-by: Vinit Agnihotri <vinit.agnihotri@gmail.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
diff --git a/drivers/mtd/ubi/build.c b/drivers/mtd/ubi/build.c
index 054a88d..08ca214 100644
--- a/drivers/mtd/ubi/build.c
+++ b/drivers/mtd/ubi/build.c
@@ -369,7 +369,7 @@
 out_wl:
 	ubi_wl_close(ubi);
 out_vtbl:
-	kfree(ubi->vtbl);
+	vfree(ubi->vtbl);
 out_si:
 	ubi_scan_destroy_si(si);
 	return err;
@@ -629,7 +629,7 @@
 out_detach:
 	ubi_eba_close(ubi);
 	ubi_wl_close(ubi);
-	kfree(ubi->vtbl);
+	vfree(ubi->vtbl);
 out_free:
 	kfree(ubi);
 out_mtd: