mm/gup: remove locked being NULL from faultin_vma_page_range()

The only caller of this function always passes in a non-NULL locked, so
just remove this obsolete comment.

Link: https://lkml.kernel.org/r/7-v2-987e91b59705+36b-gup_tidy_jgg@nvidia.com


Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Mike Rapoport (IBM) <rppt@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>