mlxsw: Enforce firmware version for Spectrum-2

In a similar fashion to Spectrum-1, enforce a specific firmware version
for Spectrum-2 so that the driver and firmware are always in sync with
regards to new features.

Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Reviewed-by: Petr Machata <petrm@mellanox.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>