use NULL getmemid segop as a shorthand for ENODEV
Instead of forcing every segment driver to implement a dummy function to
return (hopefully) ENODEV, handle NULL getmemid segop function pointer as
"return ENODEV" shorthand.

@@ -75,11 +75,10 @@
 static void     segnf_dump(struct seg *seg);
 static int      segnf_pagelock(struct seg *seg, caddr_t addr, size_t len,
                     struct page ***ppp, enum lock_type type, enum seg_rw rw);
 static int      segnf_setpagesize(struct seg *seg, caddr_t addr, size_t len,
                     uint_t szc);
-static int      segnf_getmemid(struct seg *seg, caddr_t addr, memid_t *memidp);
 
 
 struct seg_ops segnf_ops = {
         .dup            = segnf_dup,
         .unmap          = segnf_unmap,

@@ -102,11 +101,10 @@
         .advise         = (int (*)(struct seg *, caddr_t, size_t, uint_t))
                 segnf_nop,
         .dump           = segnf_dump,
         .pagelock       = segnf_pagelock,
         .setpagesize    = segnf_setpagesize,
-        .getmemid       = segnf_getmemid,
 };
 
 /*
  * vnode and page for the page of zeros we use for the nf mappings.
  */

@@ -463,12 +461,5 @@
 segnf_setpagesize(struct seg *seg, caddr_t addr, size_t len,
     uint_t szc)
 {
         return (ENOTSUP);
 }
-
-/*ARGSUSED*/
-static int
-segnf_getmemid(struct seg *seg, caddr_t addr, memid_t *memidp)
-{
-        return (ENODEV);
-}