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

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: 2aee09d8c116 ("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>