octeontx2-pf: Use memset_startat() helper in otx2_stop()

Use memset_startat() helper to simplify the code, there is no functional
change in this patch.
Signed-off-by: NXiu Jianfeng <xiujianfeng@huawei.com>
Link: https://lore.kernel.org/r/20220516092337.131653-1-xiujianfeng@huawei.comSigned-off-by: NJakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/marvell/octeontx2/nic/otx2_pf.c

@@ -1794,8 +1794,7 @@ int otx2_stop(struct net_device *netdev)
 	kfree(qset->rq);
 	kfree(qset->napi);
 	/* Do not clear RQ/SQ ringsize settings */
-	memset((void *)qset + offsetof(struct otx2_qset, sqe_cnt), 0,
-	       sizeof(*qset) - offsetof(struct otx2_qset, sqe_cnt));
+	memset_startat(qset, 0, sqe_cnt);
 	return 0;
 }
 EXPORT_SYMBOL(otx2_stop);