RDMA/mana_ib: Enable RoCE on port 1

Set netdev and RoCEv2 flag to enable GID population on port 1.
Use GIDs of the master netdev. As mc->ports[] stores slave devices,
use a helper to get the master netdev.

Signed-off-by: Konstantin Taranov <kotaranov@microsoft.com>
Link: https://lore.kernel.org/r/1712738551-22075-5-git-send-email-kotaranov@linux.microsoft.com
Signed-off-by: Leon Romanovsky <leon@kernel.org>