net/mlx4_core: Enforce irq affinity changes immediatly

During heavy traffic, napi is constatntly polling the complition queue
and no interrupt is fired. Because of that, changes to irq affinity are
ignored until traffic is stopped and resumed.

By registering to the irq notifier mechanism, and forcing interrupt when
affinity is changed, irq affinity changes will be immediatly enforced.

Signed-off-by: Yuval Atias <yuvala@mellanox.com>
Signed-off-by: Amir Vadai <amirv@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>