net/mlx5e: Enable users to change VF/PF representors carrier state

Currently PF and VF representor netdevice carrier is always controlled
by controlling the representor netdevice device state as up/down.

Representor netdevice state change undergoes one or more txq/rxq
destroy/create commands to firmware, skb and its rx buffer allocation,
health reporters creation and more.

Due to this limitation users do not have the ability to just change
the carrier of the non uplink representors without modifying the
device state.

In one use case when the eswitch physical port carrier is down/up,
user needs to update the VF link state to same as physical port
carrier.

Example of updating VF representor carrier state:
$ ip link set enp0s8f0npf0vf0 carrier off
$ ip link set enp0s8f0npf0vf0 carrier on

This enhancement results into VF link state change which is
represented by the VF representor netdevice carrier.

This enables users to modify the representor carrier without modifying
the representor netdevice state.

A simple test is run using [1] to calculate the time difference between
updating carrier vs updating device state (to update just the carrier)
with one VF to simulate 255 VFs.

Time taken to update the carrier using device up/down:
$ time ./calculate.sh dev enp0s8f0npf0vf0
real    0m30.913s
user    0m0.200s
sys     0m11.168s

Time taken to update just the carrier using carrier iproute2 command:
$ time ./calculate.sh carrier enp0s8f0npf0vf0
real    0m2.142s
user    0m0.160s
sys     0m2.021s

Test shows that its better to use carrier on/off user interface to notify
link up/down event to VF compare to device up/down interface, because
carrier user interface delivers the same event 15 times faster.

[1] https://github.com/paravmellanox/myscripts/blob/master/calculate_carrier_time.sh

Signed-off-by: Parav Pandit <parav@mellanox.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Reviewed-by: Roi Dayan <roid@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>

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