UBI: mtd/ubi/vtbl.c: fix memory leak

This patch fixes a memory leak introduced by commit
4ccf8cffa963c7b5bdc6d455ea9417084ee49aa8 and spotted by the Coverity
checker.

Signed-off-by: Adrian Bunk <[e-mail]>
Signed-off-by: Artem Bityutskiy <[e-mail]>

drivers/mtd/ubi/vtbl.c

···
 			if (ubi->autoresize_vol_id != -1) {
 				ubi_err("more then one auto-resize volume (%d "
 					"and %d)", ubi->autoresize_vol_id, i);
+				kfree(vol);
 				return -EINVAL;
 			}