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

@@ -124,11 +124,11 @@
 
 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;
+extern const struct seg_ops segdev_ops;
 
 #endif  /* _KERNEL */
 
 #ifdef  __cplusplus
 }