mm/hugetlb: unify clearing of RestoreReserve for private pages

A trivial cleanup to move clearing of RestoreReserve into adding anon rmap
of private hugetlb mappings.  It matches with the shared mappings where we
only clear the bit when adding into page cache, rather than spreading it
around the code paths.

Link: https://lkml.kernel.org/r/20221020193832.776173-1-peterx@redhat.com


Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>