sg: get rid of unused include.

sg driver does not depends on the Linuxulator any more.

Reviewed by:		imp
Differential Revision:	https://reviews.freebsd.org/D30750
MFC after:		2 weeks

sys/cam/scsi/scsi_sg.c

@@ -60,8 +60,6 @@ __FBSDID("$FreeBSD$");
 #include <cam/scsi/scsi_message.h>
 #include <cam/scsi/scsi_sg.h>
 
-#include <compat/linux/linux_ioctl.h>
-
 typedef enum {
 	SG_FLAG_LOCKED		= 0x01,
 	SG_FLAG_INVALID		= 0x02