2976 remove useless offsetof() macros

@@ -31,10 +31,11 @@
 #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 *);

@@ -327,18 +328,10 @@
 /* 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 *);