memcg: cleanup preparation for page table walk

memcg: cleanup preparation for page table walk

pagewalk.c can handle vma in itself, so we don't have to pass vma via
walk->private.  And both of mem_cgroup_count_precharge() and
mem_cgroup_move_charge() do for each vma loop themselves, but now it's
done in pagewalk.c, so let's clean up them.

Signed-off-by: Naoya Horiguchi <[email protected]>
Acked-by: Johannes Weiner <[email protected]>
Cc: "Kirill A. Shutemov" <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Cyrill Gorcunov <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Kirill A. Shutemov <[email protected]>
Cc: Pavel Emelyanov <[email protected]>
Cc: Benjamin Herrenschmidt <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>