net/mlx5: Add ConnectX-5 PCIe 4.0 to list of supported devices

Add the upcoming ConnectX-5 PCIe 4.0 device to the list of
supported devices by the mlx5 driver.

Signed-off-by: Majd Dibbiny <majd@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>