net/mlx5: Add pbmc and pptb in the port_access_reg_cap_mask

Add pbmc and pptb in the port_access_reg_cap_mask. These two
bits determine if device supports receive buffer configuration.

Signed-off-by: Huy Nguyen <huyn@mellanox.com>
Reviewed-by: Parav Pandit <parav@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>