doc: hwpoison: correct the support for hugepage

doc: hwpoison: correct the support for hugepage

The hwpoison support for huge page, both hugetlb and THP, has been in
kernel for a while, the statement in document is obsolete, correct it.

Link: https://lkml.kernel.org/r/20210819054116.266126-2-shy828301@gmail.com
Signed-off-by: Yang Shi <shy828301@gmail.com>
Acked-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Mackey <tdmackey@twitter.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>