net: mana: Fix the netdev_err()'s vPort argument in mana_init_port()

Use the correct port index rather than 0.

Signed-off-by: Dexuan Cui <decui@microsoft.com>
Reviewed-by: Haiyang Zhang <haiyangz@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>