f2fs: fix to skip shrinking extent nodes

In f2fs_shrink_extent_tree we should stop shrink flow if we have already
shrunk enough nodes in extent cache.
Signed-off-by: NChao Yu <chao2.yu@samsung.com>
Signed-off-by: NJaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/extent_cache.c

@@ -620,7 +620,7 @@ unsigned int f2fs_shrink_extent_tree(struct f2fs_sb_info *sbi, int nr_shrink)
 			write_unlock(&et->lock);
 
 			if (node_cnt + tree_cnt >= nr_shrink)
-				break;
+				goto unlock_out;
 		}
 	}
 unlock_out: