nilfs2: fix infinite loop in nilfs_palloc_freev function

After having applied commit 9954e7af ("nilfs2: add free
entries count only if clear bit operation succeeded"), a free routine
of nilfs came to fall into an infinite loop, outputting the same
message endlessly:

 nilfs_palloc_freev: entry number 29497 already freed
 nilfs_palloc_freev: entry number 29497 already freed
 nilfs_palloc_freev: entry number 29497 already freed
 nilfs_palloc_freev: entry number 29497 already freed
 nilfs_palloc_freev: entry number 29497 already freed ...

That patch broke the routine so that a loop counter is never updated
in an abnormal state.  This fixes the regression.
Signed-off-by: NRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

fs/nilfs2/alloc.c

@@ -646,7 +646,7 @@ int nilfs_palloc_freev(struct inode *inode, __u64 *entry_nrs, size_t nitems)
 	unsigned long group, group_offset;
 	int i, j, n, ret;
 
-	for (i = 0; i < nitems; i += n) {
+	for (i = 0; i < nitems; i = j) {
 		group = nilfs_palloc_group(inode, entry_nrs[i], &group_offset);
 		ret = nilfs_palloc_get_desc_block(inode, group, 0, &desc_bh);
 		if (ret < 0)