Revert "mm/hugetlb: deal with multiple calls to hugetlb_bootmem_alloc"

This reverts commit d58b2498200724e4f8c12d71a5953da03c8c8bdf.

hugetlb_bootmem_alloc() is called only once, no need to check if it was
called already at its entry.

Other checks performed during HVO initialization are also no longer
necessary because sparse_init() that calls hugetlb_vmemmap_init_early()
and hugetlb_vmemmap_init_late() is always called after
hugetlb_bootmem_alloc().

Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Acked-by: Muchun Song <muchun.song@linux.dev>