mlx5: Fix naming convention with respect to UARs

This establishes a solid naming conventions for UARs. A UAR (User Access
Region) can have size identical to a system page or can be fixed 4KB
depending on a value queried by firmware. Each UAR always has 4 blue
flame register which are used to post doorbell to send queue. In
addition, a UAR has section used for posting doorbells to CQs or EQs. In
this patch we change names to reflect this conventions.

Signed-off-by: Eli Cohen <eli@mellanox.com>
Reviewed-by: Matan Barak <matanb@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>