OS-3752 Increase IOV_MAX to at least 1024

*** 19,28 ****
--- 19,29 ----
   * CDDL HEADER END
   */
  /*
   * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
   * Use is subject to license terms.
+  * Copyright 2015 Joyent, Inc.  All rights reserved.
   */
  
  /*      Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T */
  /*        All Rights Reserved   */
  
*** 626,645 ****
  
  #ifdef _KERNEL
  /*
   * Structure for rw (read/write) procedure calls. A pointer
   * to a struiod_t is passed as a parameter to the rwnext() call.
-  *
-  * Note: DEF_IOV_MAX is defined and used as it is in "fs/vncalls.c"
-  *       as there isn't a formal definition of IOV_MAX ???
   */
- #define DEF_IOV_MAX     16
- 
  typedef struct struiod {
          mblk_t          *d_mp;          /* pointer to mblk (chain) */
          uio_t           d_uio;          /* uio info */
!         iovec_t d_iov[DEF_IOV_MAX];     /* iov referenced by uio */
  } struiod_t;
  
  /*
   * Structure for information procedure calls.
   */
--- 627,641 ----
  
  #ifdef _KERNEL
  /*
   * Structure for rw (read/write) procedure calls. A pointer
   * to a struiod_t is passed as a parameter to the rwnext() call.
   */
  typedef struct struiod {
          mblk_t          *d_mp;          /* pointer to mblk (chain) */
          uio_t           d_uio;          /* uio info */
!         iovec_t         *d_iov;         /* iov referenced by uio */
  } struiod_t;
  
  /*
   * Structure for information procedure calls.
   */