net: ethernet: ti: cpsw: add .ndo to set per-queue rate

This patch allows to rate limit queues tx queues for cpsw interface.
The rate is set in absolute Mb/s units and cannot be more a speed
an interface is connected with.

The rate for a tx queue can be tested with:

ethtool -L eth0 rx 4 tx 4

echo 100 > /sys/class/net/eth0/queues/tx-0/tx_maxrate
echo 200 > /sys/class/net/eth0/queues/tx-1/tx_maxrate
echo 50 > /sys/class/net/eth0/queues/tx-2/tx_maxrate
echo 30 > /sys/class/net/eth0/queues/tx-3/tx_maxrate

tc qdisc add dev eth0 root handle 1: multiq

tc filter add dev eth0 parent 1: protocol ip prio 1 u32 match ip\
dport 5001 0xffff action skbedit queue_mapping 0

tc filter add dev eth0 parent 1: protocol ip prio 1 u32 match ip\
dport 5002 0xffff action skbedit queue_mapping 1

tc filter add dev eth0 parent 1: protocol ip prio 1 u32 match ip\
dport 5003 0xffff action skbedit queue_mapping 2

tc filter add dev eth0 parent 1: protocol ip prio 1 u32 match ip\
dport 5004 0xffff action skbedit queue_mapping 3

iperf -c 192.168.2.1 -b 110M -p 5001 -f m -t 60
iperf -c 192.168.2.1 -b 215M -p 5002 -f m -t 60
iperf -c 192.168.2.1 -b 55M -p 5003 -f m -t 60
iperf -c 192.168.2.1 -b 32M -p 5004 -f m -t 60

Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>