f2fs: fix wrong condition check

While an orphan inode has zero link_count, f2fs_gc is able to select the inode
for foreground gc.

- f2fs_gc
 - do_garbage_collect
   - gc_data_segment
     : f2fs_iget is failed
     : get_valid_blocks() != 0, so that retry
--> here we got the infinite loop.

This patch resolved this issue.
Signed-off-by: NJaegeuk Kim <jaegeuk.kim@samsung.com>

fs/f2fs/inode.c

@@ -109,12 +109,6 @@ struct inode *f2fs_iget(struct super_block *sb, unsigned long ino)
 	ret = do_read_inode(inode);
 	if (ret)
 		goto bad_inode;
-
-	if (!sbi->por_doing && inode->i_nlink == 0) {
-		ret = -ENOENT;
-		goto bad_inode;
-	}
-
 make_now:
 	if (ino == F2FS_NODE_INO(sbi)) {
 		inode->i_mapping->a_ops = &f2fs_node_aops;