5255 uts shouldn't open-code ISP2

@@ -21,10 +21,11 @@
 /*
  * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
  * Use is subject to license terms.
  */
 
+#include <sys/sysmacros.h>
 #include <sys/systm.h>
 #include <sys/param.h>
 #include <sys/debug.h>
 #include <sys/kmem.h>
 #include <sys/group.h>

@@ -129,12 +130,11 @@
         g->grp_set[i] = NULL;
         group_pack_set(g->grp_set, g->grp_size);
         g->grp_size--;
 
         if ((gflag & GRP_RESIZE) &&
-            g->grp_size > GRP_SET_SIZE_DEFAULT &&
-            ((g->grp_size - 1) & g->grp_size) == 0)
+            g->grp_size > GRP_SET_SIZE_DEFAULT && ISP2(g->grp_size))
                 group_shrink_set(g);
 
         return (0);
 }