net/mlx5: Add HW definition of reg_c_preserve

Add capability bit to test whether reg_c value is preserved on
recirculation.

Signed-off-by: Paul Blakey <paulb@mellanox.com>
Signed-off-by: Maor Dickman <maord@nvidia.com>
Reviewed-by: Roi Dayan <roid@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>