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.comSigned-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>

mm/gup.c

@@ -1558,12 +1558,7 @@ long populate_vma_page_range(struct vm_area_struct *vma,
  * code on error (see __get_user_pages()).
  *
  * vma->vm_mm->mmap_lock must be held. The range must be page-aligned and
- * covered by the VMA.
- *
- * If @locked is NULL, it may be held for read or write and will be unperturbed.
- *
- * If @locked is non-NULL, it must held for read only and may be released.  If
- * it's released, *@locked will be set to 0.
+ * covered by the VMA. If it's released, *@locked will be set to 0.
  */
 long faultin_vma_page_range(struct vm_area_struct *vma, unsigned long start,
 			    unsigned long end, bool write, int *locked)