dm bufio: delete outdated comment

This comment was true when dm-bufio was written but, since 4.3, bios can
now have arbitrary size and the driver splits them.
Signed-off-by: NMikulas Patocka <mpatocka@redhat.com>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>

drivers/md/dm-bufio.c

@@ -540,10 +540,6 @@ static void __relink_lru(struct dm_buffer *b, int dirty)
  *
  *	the memory must be direct-mapped, not vmalloced;
  *
- *	the I/O driver can reject requests spuriously if it thinks that
- *	the requests are too big for the device or if they cross a
- *	controller-defined memory boundary.
- *
  * If the buffer is small enough (up to DM_BUFIO_INLINE_VECS pages) and
  * it is not vmalloced, try using the bio interface.
  *