hugetlbfs: s390 is always 64bit

No need to check for 64BIT. While at it, let's just select
ARCH_SUPPORTS_HUGETLBFS from arch/s390/Kconfig.

Signed-off-by: David Hildenbrand <david@redhat.com>
Link: https://lore.kernel.org/r/20210908154506.20764-1-david@redhat.com


Signed-off-by: Heiko Carstens <hca@linux.ibm.com>