net/mlx5_core: Use the the real irqn in eq->irqn

Instead of storing the msix array index in eq->irqn (vecidx),
store the real irq number.

Signed-off-by: Achiad Shochat <achiad@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>