Revert "mm: mempolicy: Let vma_merge and vma_split handle vma->vm_policy linkages"

Revert "mm: mempolicy: Let vma_merge and vma_split handle vma->vm_policy linkages"

05f144a0 ("mm: mempolicy: Let vma_merge and vma_split handle
vma->vm_policy linkages") removed vma->vm_policy updates code but it is
the purpose of mbind_range().  Now, mbind_range() is virtually a no-op and
while it does not allow memory corruption it is not the right fix.  This
patch is a revert.

[mgorman@suse.de: Edited changelog]
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Mel Gorman <mgorman@suse.de>
Cc: Christoph Lameter <cl@linux.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>