net/mlx5: EQ, Different EQ types

In mlx5 we have three types of usages for EQs,
1. Asynchronous EQs, used internally by mlx5 core for
 a. FW command completions
 b. FW page requests
 c. one EQ for all other Asynchronous events

2. Completion EQs, used for CQ completion (we create one per core)

3. *Special type of EQ (page fault) used for RDMA on demand paging
(ODP).

*The 3rd type shouldn't be special at least in mlx5 core, it is yet
another async events EQ with specific use case, it will be removed in
the next two patches, and will completely move its logic to mlx5_ib,
as it is rdma specific.

In this patch we remove use case (eq type) specific fields from
struct mlx5_eq into a new eq type specific structures.

struct mlx5_eq_async;
truct mlx5_eq_comp;
struct mlx5_eq_pagefault;

Separate between their type specific flows.

In the future we will allow users to create there own generic EQs.
for now we will allow only one for ODP in next patches.

We will introduce event listeners registration API for those who
want to receive mlx5 async events.
After that mlx5 eq handling will be clean from feature/user specific
handling.

Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>
Reviewed-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>