mlx4: do not call napi_schedule() without care

Disable BH around the call to napi_schedule() to avoid following warning

[   52.095499] NOHZ: local_softirq_pending 08
[   52.421291] NOHZ: local_softirq_pending 08
[   52.608313] NOHZ: local_softirq_pending 08

Fixes: 8d59de8f

 ("net/mlx4_en: Process all completions in RX rings after port goes up")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Erez Shitrit <erezsh@mellanox.com>
Cc: Eugenia Emantayev <eugenia@mellanox.com>
Cc: Tariq Toukan <tariqt@mellanox.com>
Acked-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>