6153 use NULL pagelock segop as a shorthand for ENOTSUP

@@ -1972,10 +1972,13 @@
 
 int
 segop_pagelock(struct seg *seg, caddr_t addr, size_t len, struct page ***page,
     enum lock_type type, enum seg_rw rw)
 {
+        if (seg->s_ops->pagelock == NULL)
+                return (ENOTSUP);
+
         return (seg->s_ops->pagelock(seg, addr, len, page, type, rw));
 }
 
 int
 segop_setpagesize(struct seg *seg, caddr_t addr, size_t len, uint_t szc)