netdevice: shrink size of struct netdev_queue

- trans_timeout is incremented when tx queue timed out (tx watchdog).
- tx_maxrate is set via sysfs

Moving tx_maxrate to read-mostly part shrinks the struct by 64 bytes.
While at it, also move trans_timeout (it is out-of-place in the
'write-mostly' part).

Signed-off-by: Florian Westphal <fw@strlen.de>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>