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

@@ -92,11 +92,11 @@
 /* segkpm support */
 static caddr_t  segmap_pagecreate_kpm(struct seg *, vnode_t *, u_offset_t,
                         struct smap *, enum seg_rw);
 struct smap     *get_smap_kpm(caddr_t, page_t **);
 
-static struct seg_ops segmap_ops = {
+static const struct seg_ops segmap_ops = {
         .free           = segmap_free,
         .fault          = segmap_fault,
         .faulta         = segmap_faulta,
         .checkprot      = segmap_checkprot,
         .kluster        = segmap_kluster,