GCC4.6: Squash warning in vmt.c

vmt.c: In function ‘ubi_free_volume’:
vmt.c:681:6: warning: variable ‘err’ set but not used
[-Wunused-but-set-variable]

Signed-off-by: Marek Vasut <marek.vasut@gmail.com>
Acked-by: Mike Frysinger <vapier@gentoo.org>
diff --git a/drivers/mtd/ubi/vmt.c b/drivers/mtd/ubi/vmt.c
index 061da64..ce9fec7 100644
--- a/drivers/mtd/ubi/vmt.c
+++ b/drivers/mtd/ubi/vmt.c
@@ -678,12 +678,10 @@
  */
 void ubi_free_volume(struct ubi_device *ubi, struct ubi_volume *vol)
 {
-	int err;
-
 	dbg_msg("free volume %d", vol->vol_id);
 
 	ubi->volumes[vol->vol_id] = NULL;
-	err = ubi_destroy_gluebi(vol);
+	ubi_destroy_gluebi(vol);
 	cdev_del(&vol->cdev);
 	volume_sysfs_close(vol);
 }