mm/hmm: do not check pmd_protnone twice in hmm_vma_handle_pmd()

pmd_to_hmm_pfn_flags() already checks it and makes the cpu flags 0. If no
fault is requested then the pfns should be returned with the not valid
flags.

It should not unconditionally fault if faulting is not requested.

Fixes: 2aee09d ("mm/hmm: change hmm_vma_fault() to allow write fault on page basis")
Reviewed-by: Ralph Campbell <rcampbell@nvidia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

mm/hmm.c

@@ -226,7 +226,7 @@ static int hmm_vma_handle_pmd(struct mm_walk *walk, unsigned long addr,
 	hmm_range_need_fault(hmm_vma_walk, pfns, npages, cpu_flags,
 			     &fault, &write_fault);
 
-	if (pmd_protnone(pmd) || fault || write_fault)
+	if (fault || write_fault)
 		return hmm_vma_walk_hole_(addr, end, fault, write_fault, walk);
 
 	pfn = pmd_pfn(pmd) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);