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

*** 1883,1893 ****
          i = 2;
          for (seg = AS_SEGFIRST(as); seg != NULL; seg = AS_SEGNEXT(as, seg)) {
                  caddr_t eaddr = seg->s_base + pr_getsegsize(seg, 0);
                  caddr_t saddr, naddr;
                  void *tmp = NULL;
!                 extern struct seg_ops segspt_shmops;
  
                  for (saddr = seg->s_base; saddr < eaddr; saddr = naddr) {
                          uint_t prot;
                          size_t size;
                          int type;
--- 1883,1893 ----
          i = 2;
          for (seg = AS_SEGFIRST(as); seg != NULL; seg = AS_SEGNEXT(as, seg)) {
                  caddr_t eaddr = seg->s_base + pr_getsegsize(seg, 0);
                  caddr_t saddr, naddr;
                  void *tmp = NULL;
!                 extern const struct seg_ops segspt_shmops;
  
                  for (saddr = seg->s_base; saddr < eaddr; saddr = naddr) {
                          uint_t prot;
                          size_t size;
                          int type;