net/mlx4_en: Process all completions in RX rings after port goes up

Currently there is a race between incoming traffic and
initialization flow. HW is able to receive the packets
after INIT_PORT is done and unicast steering is configured.
Before we set priv->port_up NAPI is not scheduled and
receive queues become full. Therefore we never get
new interrupts about the completions.
This issue could happen if running heavy traffic during
bringing port up.
The resolution is to schedule NAPI once port_up is set.
If receive queues were full this will process all cqes
and release them.

Fixes: c27a02cd ("mlx4_en: Add driver for Mellanox ConnectX 10GbE NIC")
Signed-off-by: Erez Shitrit <erezsh@mellanox.com>
Signed-off-by: Eugenia Emantayev <eugenia@mellanox.com>
Signed-off-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>