qcow2: remove a line of unnecessary code

Commit 3948d1d4 removed the pointer argument we filled in with l2_offset
but forgot to remove the unnecessary l2_offset assignment.
Signed-off-by: NZhi Yong Wu <wuzhy@linux.vnet.ibm.com>
Reviewed-by: NStefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

block/qcow2-cluster.c

@@ -540,7 +540,6 @@ static int get_cluster_table(BlockDriverState *bs, uint64_t offset,
         if (l2_offset) {
             qcow2_free_clusters(bs, l2_offset, s->l2_size * sizeof(uint64_t));
         }
-        l2_offset = s->l1_table[l1_index] & L1E_OFFSET_MASK;
     }
 
     /* find the cluster offset for the given disk offset */