common/mlx5: fix redundant field in MR control structure

common/mlx5: fix redundant field in MR control structure

Inside the MR control structure there is a pointer to the common device.
This pointer enables access to the global cache as well as hardware
objects that may be required in case a new MR needs to be created.

The purpose of adding this pointer into the MR control structure was to
avoid its transfer as a parameter to all the functions of searching MR
in the caches.
However, adding it to this structure increased the Rx and Tx data-path
structures, all the fields that followed it were slightly moved away
which caused to a reduction in performance.

This patch removes the pointer from the structure. It can be accessed
through the "dev_gen_ptr" existing field using the "container_of"
operator.

Fixes: 334ed198ab4d ("common/mlx5: remove redundant parameter in MR search")
Signed-off-by: Michael Baum <michaelba@nvidia.com>
Acked-by: Matan Azrad <matan@nvidia.com>