net/mlx5: Change interrupt handler to call chain notifier

Multiple EQs may share the same IRQ in subsequent patches.

Instead of calling the IRQ handler directly, the EQ will register
to an atomic chain notfier.

The Linux built-in shared IRQ is not used because it forces the caller
to disable the IRQ and clear affinity before free_irq() can be called.

This patch is the first step in the separation of IRQ and EQ logic.

Signed-off-by: Yuval Avnery <yuvalav@mellanox.com>
Reviewed-by: Parav Pandit <parav@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>

include/linux/mlx5/eq.h

@@ -26,8 +26,7 @@ struct mlx5_eq_param {
 	u8             index;
 	int            nent;
 	u64            mask;
-	void          *context;
-	irq_handler_t  handler;
+	struct notifier_block *nb;
 };
 
 struct mlx5_eq *