mm/huge_memory: convert do_huge_pmd_anonymous_page() to use vma_alloc_folio()

Remove the use of this old API, eliminating a call to
prep_transhuge_page().

Link: https://lkml.kernel.org/r/20220504182857.4013401-3-willy@infradead.org


Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>