macvtap: remove useless codes in macvtap_aio_read() and macvtap_recvmsg()

By checking related codes, it is impossible that ret > len or total_len,
so we should remove some useless coeds in both above functions.
Signed-off-by: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/macvtap.c

@@ -871,7 +871,6 @@ static ssize_t macvtap_aio_read(struct kiocb *iocb, const struct iovec *iv,
 	}
 
 	ret = macvtap_do_read(q, iv, len, file->f_flags & O_NONBLOCK);
-	ret = min_t(ssize_t, ret, len); /* XXX copied from tun.c. Why? */
 	if (ret > 0)
 		iocb->ki_pos = ret;
 out:
@@ -1106,10 +1105,6 @@ static int macvtap_recvmsg(struct kiocb *iocb, struct socket *sock,
 		return -EINVAL;
 	ret = macvtap_do_read(q, m->msg_iov, total_len,
 			  flags & MSG_DONTWAIT);
-	if (ret > total_len) {
-		m->msg_flags |= MSG_TRUNC;
-		ret = flags & MSG_TRUNC ? ret : total_len;
-	}
 	return ret;
 }