net/mlx5: Read MCAM register groups 1 and 2

On load, Driver caches MCAM (Management Capabilities Mask Register)
registers. in addition to the only MCAM register group (0) the driver
already reads, here we add support for reading groups 1 and 2.

Signed-off-by: Eran Ben Elisha <eranbe@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>