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>