Initialise scatter/gather list in sg driver

After turning on DEBUG_SG I hit a fail:

kernel BUG at include/linux/scatterlist.h:50!

	sg_build_indirect
	sg_build_reserve
	sg_open
	chrdev_open
	__dentry_open
	do_filp_open
	do_sys_open

We should initialise the sg list when we allocate it in sg_build_sgat.
Signed-off-by: NAnton Blanchard <anton@samba.org>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

drivers/scsi/sg.c

@@ -1652,6 +1652,7 @@ sg_build_sgat(Sg_scatter_hold * schp, const Sg_fd * sfp, int tablesize)
 	schp->buffer = kzalloc(sg_bufflen, gfp_flags);
 	if (!schp->buffer)
 		return -ENOMEM;
+	sg_init_table(schp->buffer, tablesize);
 	schp->sglist_len = sg_bufflen;
 	return tablesize;	/* number of scat_gath elements allocated */
 }