arch/powerpc: teach book3s64 arch_get_unmapped_area{_topdown} to handle hugetlb mappings

arch/powerpc: teach book3s64 arch_get_unmapped_area{_topdown} to handle hugetlb mappings

We want to stop special casing hugetlb mappings and make them go through
generic channels, so teach arch_get_unmapped_area{_topdown} to handle
those.

Reshuffle file_to_psize() definition so arch_get_unmapped_area{_topdown}
can make use of it.

Link: https://lkml.kernel.org/r/20241007075037.267650-6-osalvador@suse.de
Signed-off-by: Oscar Salvador <osalvador@suse.de>
Cc: David Hildenbrand <david@redhat.com>
Cc: Donet Tom <donettom@linux.ibm.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Peter Xu <peterx@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>