use NULL capable segop as a shorthand for no-capabilities
Instead of forcing every segment driver to implement a dummy "return 0"
function, handle NULL capable segop function pointer as "no copabilities
supported" shorthand.

@@ -86,11 +86,10 @@
 static void     segmap_dump(struct seg *seg);
 static int      segmap_pagelock(struct seg *seg, caddr_t addr, size_t len,
                         struct page ***ppp, enum lock_type type,
                         enum seg_rw rw);
 static int      segmap_getmemid(struct seg *seg, caddr_t addr, memid_t *memidp);
-static int      segmap_capable(struct seg *seg, segcapability_t capability);
 
 /* 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 **);

@@ -106,11 +105,10 @@
         .gettype        = segmap_gettype,
         .getvp          = segmap_getvp,
         .dump           = segmap_dump,
         .pagelock       = segmap_pagelock,
         .getmemid       = segmap_getmemid,
-        .capable        = segmap_capable,
 };
 
 /*
  * Private segmap routines.
  */

@@ -2166,17 +2164,10 @@
         memidp->val[0] = (uintptr_t)smd->smd_sm->sm_vp;
         memidp->val[1] = smd->smd_sm->sm_off + (uintptr_t)(addr - seg->s_base);
         return (0);
 }
 
-/*ARGSUSED*/
-static int
-segmap_capable(struct seg *seg, segcapability_t capability)
-{
-        return (0);
-}
-
 
 #ifdef  SEGKPM_SUPPORT
 
 /*
  * segkpm support routines