const-ify make segment ops structures
There is no reason to keep the segment ops structures writable.

*** 756,766 ****
          if (capability == S_CAPABILITY_NOMINFLT)
                  return (1);
          return (0);
  }
  
! static struct seg_ops segkmem_ops = {
          .fault          = segkmem_fault,
          .setprot        = segkmem_setprot,
          .checkprot      = segkmem_checkprot,
          .kluster        = segkmem_kluster,
          .dump           = segkmem_dump,
--- 756,766 ----
          if (capability == S_CAPABILITY_NOMINFLT)
                  return (1);
          return (0);
  }
  
! static const struct seg_ops segkmem_ops = {
          .fault          = segkmem_fault,
          .setprot        = segkmem_setprot,
          .checkprot      = segkmem_checkprot,
          .kluster        = segkmem_kluster,
          .dump           = segkmem_dump,