mm: remove unneeded PageAnon check in restore_exclusive_pte()

When code reaches here, the page must be !PageAnon.  There's no need to
check PageAnon again.  Remove it.

Link: https://lkml.kernel.org/r/20220716081816.10752-1-linmiaohe@huawei.com


Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>