2976 remove useless offsetof() macros

*** 31,40 ****
--- 31,41 ----
  #ifdef __cplusplus
  extern "C" {
  #endif
  
  #include <sys/sunldi.h>
+ #include <sys/sysmacros.h>
  #include <sys/usb/usba/usbai_private.h>
  
  
  int usb_ac_open(dev_info_t *);
  void usb_ac_close(dev_info_t *);
*** 327,344 ****
  /* value for acp_driver */
  #define USB_AS_PLUMBED  1
  #define USB_AH_PLUMBED  2
  #define UNKNOWN_PLUMBED 3
  
- /* other useful macros */
- #define offsetof(s, m)  ((size_t)(&(((s *)0)->m)))
- 
- 
- 
- 
- 
- 
  #define AF_REGISTERED   0x1
  #define AD_SETUP        0x10
  
  
  int usb_audio_attach(usb_ac_state_t *);
--- 328,337 ----