5255 uts shouldn't open-code ISP2

*** 22,31 ****
--- 22,32 ----
   * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
   * Copyright (c) 2011, 2014 by Delphix. All rights reserved.
   * Copyright (c) 2011 Nexenta Systems, Inc. All rights reserved.
   */
  
+ #include <sys/sysmacros.h>
  #include <sys/zfs_context.h>
  #include <sys/fm/fs/zfs.h>
  #include <sys/spa.h>
  #include <sys/txg.h>
  #include <sys/spa_impl.h>
*** 117,127 ****
                  size_t size = (c + 1) << SPA_MINBLOCKSHIFT;
                  size_t p2 = size;
                  size_t align = 0;
                  size_t cflags = (size > zio_buf_debug_limit) ? KMC_NODEBUG : 0;
  
!                 while (p2 & (p2 - 1))
                          p2 &= p2 - 1;
  
  #ifndef _KERNEL
                  /*
                   * If we are using watchpoints, put each buffer on its own page,
--- 118,128 ----
                  size_t size = (c + 1) << SPA_MINBLOCKSHIFT;
                  size_t p2 = size;
                  size_t align = 0;
                  size_t cflags = (size > zio_buf_debug_limit) ? KMC_NODEBUG : 0;
  
!                 while (!ISP2(p2))
                          p2 &= p2 - 1;
  
  #ifndef _KERNEL
                  /*
                   * If we are using watchpoints, put each buffer on its own page,