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

@@ -203,12 +203,12 @@
 #define P_HASHWIRED_MASK                (seg_phashsize_wired - 1)
 #define P_BASESHIFT                     (6)
 
 kthread_t *seg_pasync_thr;
 
-extern struct seg_ops segvn_ops;
-extern struct seg_ops segspt_shmops;
+extern const struct seg_ops segvn_ops;
+extern const struct seg_ops segspt_shmops;
 
 #define IS_PFLAGS_WIRED(flags) ((flags) & SEGP_FORCE_WIRED)
 #define IS_PCP_WIRED(pcp) IS_PFLAGS_WIRED((pcp)->p_flags)
 
 #define LBOLT_DELTA(t)  ((ulong_t)(ddi_get_lbolt() - (t)))