staging: wfx: associate tx_queues to vifs

staging: wfx: associate tx_queues to vifs

The device handles 4 queues (one per AC) for each virtual interface (and
maximum 4 virtual interfaces). Until now the driver unified the queue of
all interfaces and handled only 4 queues for whole device.

This architecture did not allow to balance the traffic between the vif. So,
this patch relocate the queues into the vif and change the API accordingly.

Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Link: https://lore.kernel.org/r/20200701150707.222985-2-Jerome.Pouiller@silabs.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>