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

*** 124,134 ****
  
  extern int segdev_create(struct seg *, void *);
  
  extern int segdev_copyto(struct seg *, caddr_t, const void *, void *, size_t);
  extern int segdev_copyfrom(struct seg *, caddr_t, const void *, void *, size_t);
! extern struct seg_ops segdev_ops;
  
  #endif  /* _KERNEL */
  
  #ifdef  __cplusplus
  }
--- 124,134 ----
  
  extern int segdev_create(struct seg *, void *);
  
  extern int segdev_copyto(struct seg *, caddr_t, const void *, void *, size_t);
  extern int segdev_copyfrom(struct seg *, caddr_t, const void *, void *, size_t);
! extern const struct seg_ops segdev_ops;
  
  #endif  /* _KERNEL */
  
  #ifdef  __cplusplus
  }