use NULL dump segop as a shorthand for no-op
Instead of forcing every segment driver to implement a dummy function that
does nothing, handle NULL dump segop function pointer as a no-op shorthand.

@@ -100,18 +100,16 @@
 /*
  * Private seg op routines.
  */
 faultcode_t segkpm_fault(struct hat *hat, struct seg *seg, caddr_t addr,
                         size_t len, enum fault_type type, enum seg_rw rw);
-static void     segkpm_dump(struct seg *);
 static int      segkpm_pagelock(struct seg *seg, caddr_t addr, size_t len,
                         struct page ***page, enum lock_type type,
                         enum seg_rw rw);
 
 static const struct seg_ops segkpm_ops = {
         .fault          = segkpm_fault,
-        .dump           = segkpm_dump,
         .pagelock       = segkpm_pagelock,
 //#ifndef SEGKPM_SUPPORT
 #if 0
 #error FIXME: define nop
         .dup            = nop,

@@ -316,14 +314,5 @@
 segkpm_pagelock(struct seg *seg, caddr_t addr, size_t len,
         struct page ***page, enum lock_type type, enum seg_rw rw)
 {
         return (ENOTSUP);
 }
-
-/*
- * segkpm pages are not dumped, so we just return
- */
-/*ARGSUSED*/
-static void
-segkpm_dump(struct seg *seg)
-{
-}