hwpoison: rename CONFIG

CONFIG_HUGETLBFS controls hugetlbfs interface code.
OTOH, CONFIG_HUGETLB_PAGE controls hugepage management code.
So we should use CONFIG_HUGETLB_PAGE here.

Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>