mm/swap: fix the obsolete comment for SWP_TYPE_SHIFT

Since commit 3159f94 ("xarray: Replace exceptional entries"), there
is only one bit of 'type' can be shifted up.  Update the corresponding
comment.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Miaohe Lin <[email protected]>
Reviewed-by: David Hildenbrand <[email protected]>
Cc: Alistair Popple <[email protected]>
Cc: David Howells <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Naoya Horiguchi <[email protected]>
Cc: NeilBrown <[email protected]>
Cc: Peter Xu <[email protected]>
Cc: Suren Baghdasaryan <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: Oscar Salvador <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

include/linux/swapops.h

@@ -13,10 +13,10 @@
  * get good packing density in that tree, so the index should be dense in
  * the low-order bits.
  *
- * We arrange the `type' and `offset' fields so that `type' is at the seven
+ * We arrange the `type' and `offset' fields so that `type' is at the six
  * high-order bits of the swp_entry_t and `offset' is right-aligned in the
  * remaining bits.  Although `type' itself needs only five bits, we allow for
- * shmem/tmpfs to shift it all up a further two bits: see swp_to_radix_entry().
+ * shmem/tmpfs to shift it all up a further one bit: see swp_to_radix_entry().
  *
  * swp_entry_t's are *never* stored anywhere in their arch-dependent format.
  */