f2fs: use list_for_each_entry rather than list_for_each_entry_safe

We can do this, since now we use a global mutex, f2fs_stat_mutex to protect its
list operations.

Signed-off-by: Jianpeng Ma <majianpeng@gmail.com>
[Jaegeuk Kim: add description]
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>

fs/f2fs/debug.c

@@ -175,12 +175,12 @@ get_cache:
 
 static int stat_show(struct seq_file *s, void *v)
 {
-	struct f2fs_stat_info *si, *next;
+	struct f2fs_stat_info *si;
 	int i = 0;
 	int j;
 
 	mutex_lock(&f2fs_stat_mutex);
-	list_for_each_entry_safe(si, next, &f2fs_stat_list, stat_list) {
+	list_for_each_entry(si, &f2fs_stat_list, stat_list) {
 		char devname[BDEVNAME_SIZE];
 
 		update_general_status(si->sbi);