f2fs: use list_for_each_entry rather than list_for_each_entry_safe
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 <c2efc80ba27cf31d4676f82b7232757b76911f7a@gmail.com>
[Jaegeuk Kim: add description]
Signed-off-by: Jaegeuk Kim <20424effba9d4aeeb410130c5f23aa328fa29e09@samsung.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs