selftests: mlxsw: Check line card info on provisioned line card

Once line card is provisioned, check if HW revision and INI version
are exposed.

Signed-off-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>