Btrfs: kill unused code in btrfs_search_forward

After commit de78b51a2852bddccd6535e9e12de65f92787a1e
(btrfs: remove cache only arguments from defrag path), @blockptr is no more
used.

Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>

fs/btrfs/ctree.c

@@ -4914,10 +4914,8 @@ again:
 		 * If it is too old, old, skip to the next one.
 		 */
 		while (slot < nritems) {
-			u64 blockptr;
 			u64 gen;
 
-			blockptr = btrfs_node_blockptr(cur, slot);
 			gen = btrfs_node_ptr_generation(cur, slot);
 			if (gen < min_trans) {
 				slot++;