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.

@@ -104,17 +104,15 @@
                         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 int      segkpm_capable(struct seg *, segcapability_t);
 
 static struct seg_ops segkpm_ops = {
         .fault          = segkpm_fault,
         .dump           = segkpm_dump,
         .pagelock       = segkpm_pagelock,
-        .capable        = segkpm_capable,
 //#ifndef SEGKPM_SUPPORT
 #if 0
 #error FIXME: define nop
         .dup            = nop,
         .unmap          = nop,

@@ -329,15 +327,5 @@
 /*ARGSUSED*/
 static void
 segkpm_dump(struct seg *seg)
 {
 }
-
-/*
- * We claim to have no special capabilities.
- */
-/*ARGSUSED*/
-static int
-segkpm_capable(struct seg *seg, segcapability_t capability)
-{
-        return (0);
-}