mm/rmap: rename anon_vma_unlock() => anon_vma_unlock_write()

mm/rmap: rename anon_vma_unlock() => anon_vma_unlock_write()

comment in 4fc3f1d66b1ef0d ("mm/rmap, migration: Make rmap_walk_anon() and
try_to_unmap_anon() more scalable") says:

| Rename anon_vma_[un]lock() => anon_vma_[un]lock_write(),
| to make it clearer that it's an exclusive write-lock in
| that case - suggested by Rik van Riel.

But that commit renames only anon_vma_lock()

Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Cc: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>