net/memif: support multiple Tx

net/memif: support multiple Tx

When Multiple slave/master Memif's interfaces are created in single
process data transmission over second connection is not successful.

Issue is because of "mq->in_port" is not initialized with
"dev->data->port_id" in memif_tx_queue_setup() function, and while
transmitting packets over second connection in eth_memif_tx function
it refer "mq->in_port" which is always zero, which leads to data
transmission always in 0th port.

To mitigate the issue,"mq->in_port" is initialized with
"dev->data->port_id" in memif_tx_queue_setup() function.

Signed-off-by: Anand Sunkad <anand.sunkad@benisontech.com>
Reviewed-by: Jakub Grajciar <jgrajcia@cisco.com>