mm, hugetlb, hwpoison: separate branch for free and in-use hugepage

We know that HPageFreed pages should have page refcount 0, so
get_page_unless_zero() always fails and returns 0.  So explicitly separate
the branch based on page state for minor optimization and better
readability.

Link: https://lkml.kernel.org/r/20220415041848.GA3034499@ik1-406-35019.vs.sakura.ne.jp


Signed-off-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Suggested-by: Mike Kravetz <mike.kravetz@oracle.com>
Suggested-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>