net/mlx4: drop MAC flows affecting all Rx queues

net/mlx4: drop MAC flows affecting all Rx queues

Configuring several Rx queues enables RSS, which causes an additional
special parent queue to be created to manage them.

MAC flows are associated with the queue supposed to receive packets; either
the parent one in case of RSS or the single orphan otherwise.

For historical reasons the current implementation supports another scenario
with multiple orphans, in which case MAC flows are configured on all of
them. This is harmless but useless since it cannot happen.

Removing this feature allows dissociating the remaining MAC flow from Rx
queues and store it inside the private structure where it belongs.

Signed-off-by: Adrien Mazarguil <adrien.mazarguil@6wind.com>